Composite Interfaces
ISSN: 0927-6440 (Print) 1568-5543 (Online) Journal homepage: https://www.tandfonline.com/loi/tcoi20
A review on innovations in polymeric
nanocomposite packaging materials and electrical
sensors for food and agriculture
C. I. Idumah, M. Zurina, J. Ogbu, J. U. Ndem & E. C. Igba
To cite this article: C. I. Idumah, M. Zurina, J. Ogbu, J. U. Ndem & E. C. Igba (2019): A review on
innovations in polymeric nanocomposite packaging materials and electrical sensors for food and
agriculture, Composite Interfaces, DOI: 10.1080/09276440.2019.1600972
To link to this article: https://doi.org/10.1080/09276440.2019.1600972
Published online: 23 May 2019.
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COMPOSITE INTERFACES
https://doi.org/10.1080/09276440.2019.1600972
A review on innovations in polymeric nanocomposite
packaging materials and electrical sensors for food and
agriculture
C. I. Idumah
a
, M. Zurinab, J. Ogbua, J. U. Ndema and E. C. Igbaa
a
Technical and Vocational, Ebonyi State University, Abakaliki, Nigeria; bEnhanced Polymer Research Group
(EnPRO), Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi
Malaysia, Skudai, Malaysia
ABSTRACT
ARTICLE HISTORY
The application of polymer nanocomposites packaging materials in
industrial, food and agricultural products is a superior alternative to
traditional packaging materials such as glass, paper, and metals due to
their functionalization, flexibility, and minimal cost. However, usage of
these materials has been hindered due to their inferior mechanical and
barrier behaviors, which are susceptible to improvement through
inclusion of functionalized reinforcing macro- or nanofillers.
Furthermore, most reinforced materials exhibit inferior matrix–filler
interfacial interactions, which are enhanced with reducing filler dimensions. Hence, this review elucidates functionalization of composites
interfacial interaction and its relationship to enhancement of the
properties of packaging materials, especially antimicrobial tendencies,
enzyme immobilization behavior, biosensing affinity, and so on. Thus,
a fundamental understanding of interfacial structure and its relationship to the overall improvement of properties are presented.
Therefore, nanomaterials, such as cellulose, nanoclay, halloysite nanotubes, carbon allotropes (graphene and carbon nanotubes), silica, and
so on, are discussed relative to their surface treatment approaches and
effects on composites films properties for effective packaging.
Recently, emerging innovations in nanostructured polymeric composite materials and electrical-sensors, their current applications and
future outlook as food, agricultural and industrial packaging materials
are also herewith elucidated.
Received 6 December 2018
Accepted 26 March 2019
CONTACT C. I. Idumah
idugoldengate@yahoo.com
© 2019 Informa UK Limited, trading as Taylor & Francis Group
KEYWORDS
Polymer nanocomposites;
interfacial interactions;
nano-sensors; biosensors
Ebonyi State University, Abakaliki, Nigeria
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1. Introduction
Biosensing technology with regard to nanomaterials is the most prospective electrically
inclined device utilized in dealing with environmental, health, and energy challenges
across the globe [1,2]. Nanomaterials are classified as particles containing less than
100 nm in at least a dimension of its size [3]. These nanomaterials include metallic-,
metallicoxide-, and carbon-oriented polymers possessing biocomposite properties.
Various types of nanoparticles (NPs) have undergone development including zinc
oxide (ZnO), titanium dioxide (TiO2), magnetic iron, aluminum, copper, silver, zinc,
cerium oxide, and silica nanoparticles (nSiO2), in addition to single or multiple walled
carbon nanotubes (MWCNTs) [4–7].
The development of nanotechnology in agriculture has extended to various fields
such as crop protection, food production, toxin and pathogen exposure, water purification, environmental remediation, food packaging, and wastewater treatment. A topnotch emerging nanomaterials application in biosensing is in analytical chemistry,
which performs a quality control measure in food analysis. The inclusion of nanomaterials in chemical analysis enhances their specificity, sensitivity, and detection limits in
attainment of femto-molar degree of detection. Their utilization in biosensor technology enables rapid detection of agricultural pathogens [8–11].
Biosensors based on nanomaterials are perceived as topnotch tools with rapid,
easier, and less cost solutions in comparison with established technologies such as
electrochemical, fluorescence, ultraviolet (UV)-Vis and high-performance liquid
chromatography. Presently, most materials utilized in food packaging exhibit undegradability, thereby causing a critical global environmental challenge. Novel biooriented materials have been utilized in developing edible and biodegradable films
as huge effort has been made at extending shelf life and improving quality of food
while simultaneously reducing packaging waste [12]. However, utilization of edible
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and biodegradable polymers has been hindered due to challenges concerning performance such as brittleness, poor gas and moisture resistivity, processing flaws such as
poor heat distortion temperature, and cost [13]. Nanotechnological applications to
these polymers show prospects of opening new prospects for enhancing both properties and low-cost attributes of these materials [14].
Numerous nanocomposites have undergone development through inclusion of
reinforcing fillers in polymers to improve their thermal, mechanical, and barrier
properties. Majority of these reinforcing materials cause inferior interactions at the
interface of both components. In previous decades, use of polymeric materials in food
packaging has tremendously increased as result of their benefits over other traditional
materials [15–27].
Globally, polymer market has increased from about 5 million tons in the 1950s to
over a 100 million tons presently, with packaging representing about 42% as shown in
Figure 1, and positing about 2% of gross national product in advanced countries [1].
Polymer packaging offers numerous properties including resistance to food spoilage
and flexibility, barrier to oxygen and moisture, strength and stiffness [28–33].
Macroscopic reinforcing substrates commonly contain flaws, which become less
significant as the particles of the reinforcement fillers reduce in dimension [34].
Polymer composites are composition of polymers containing inorganic or organic
fillers with peculiar geometries such as fibers, flakes, spheres, and particulates [35].
The utilization of fillers (NPs) exhibiting at least a single dimension in the nanometric
range results in polymer nanocomposites (PNC) [36]. Three types of fillers can be
differentiated based on the scope of dimensions existing in the nanometric range. Thus,
iso-dimensional NPs, including spherical nSiO2 or semiconductor nanoclusters, exhibit
three nanometric dimensions [37]. Nanotubes or whiskers exhibit structural elongation
where two dimensions are in the nanometric scale, while the third is larger. Polymericlayered crystal nanocomposites occur when only a single dimension is exhibited in the
nanometric range via polymer intercalation or when a monomer undergoes polymerization in the interior of the layered host crystal galleries [38].
A uniform distribution of NPs results in very large matrix/filler interfacial area, with
variation in molecular mobility, relaxation behavior, and thermal and mechanical
behaviors of the material. Fillers exhibiting elevated ratio in largest to the smallest
dimension (i.e., aspect ratio) are specifically interesting due to their high specific surface
Figure 1. Polymer global market.
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C. I. IDUMAH ET AL.
area, which enhances superior reinforcement effects [15–27,39]. Moreover, apart from
reinforcement NPs, which exhibit functions of enhancing mechanical and barrier
properties of the packaging materials, there are other types of nanostructures which
are responsible for other functions, such as inculcation of active or smart behaviors in
the packaging materials such as biosensing, antimicrobial activity, enzyme immobilization, and so on.
In present paper, widely investigated NPs will be showcased relative to their basic
functions/applications in food packaging materials. Some particles exhibit numerous
applications, which sometimes overlap, such as immobilized enzymes with capability of
acting as antimicrobial parts, oxygen scavengers, and/or biosensors. A schematic elucidation of packaging life cycle is shown in Figure 2.
2. General overview of packaging materials
2.1. Glass
The merits of glass as a packaging material include chemical inertness, transparency,
heat barrier, impermeability, stiffness, and overall consumer attraction. The flaws in
glass application include weight and fragility. Soda-lime glass is the main material
applied in producing glassware such as jars and bottles used for packaging food [40].
The typical compositions of soda-lime glass are Na2O (12–15%), SiO2 (68–73%), CaO
(10–13%), and other oxides in smaller proportions [41]. Jars or bottles made from glass
are specifically customized for peculiar applications. Similar to plastics, glassware can be
reused or recycled. However, in comparison to metals, glasses are standardized to a
lesser degree.
Glass packaging is enabling brands to have a versatile range of design line [42]. For
instance, exclusive designs peculiar to glass packaging facilitate unique product identification for wine and spirits brands. Glass bottles composed of thickened bases,
decoration and embossing work in conjunction with labeling designs in hindering a
coordinated, high-quality image which provides shelf-presence and effectively represents the brand and product message. In addition, glass is eco-benign and due to its
Figure 2. Packaging life cycle.
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origination from sand it is marine-life friendly. Glasswares are generally recyclable, safe,
and devoid of toxicity [43].
The market trend of glass reveals that consumers taste for premium, healthy, and
sustainable services which glass packaging offers remains significant. According to a
2017 EcoFocus Worldwide (ecofocusworldwide.com) survey of consumers in USA, it
was revealed that 90% accept that glass packages preserve and protect food and
beverages flavor [44]. Thus, 55% of consumers’ ranked glass packaging higher over all
other types of packaging relative to health considerations, with cans ranked 30% and
plastic bottles 18%.
2.2. Paper
Accruable benefits of paper used as packaging material include mechanical strength,
cheap pricing, printability, versatility, and low weight. Paper is primarily applied in
packaging as wrapping material, boxes, and pouches, in addition to its application as
secondary packaging materials such as cartons and corrugated-cardboard boxes [45].
Packaging materials which are laminated are mainly composed of paper. The main
deficiency of paper use is its susceptibility to moisture. However, paper permeability to
fat and moisture can be minimized by coating with wax and referred as waxed-paper.
Nevertheless, paper wares are mostly applied in food packaging. Paper characteristics
can be altered through the process of manufacture, pulp composition, and varying
surface modifications.
Plain paper is usually not heat-sealable and exhibits poor barrier tendencies and
hence not utilized in long-term food protection. During application as primary packaging, paper usually undergoes treating, coating, lamination, or impregnation using
materials such as resins, lacquers, waxes with the aim of improving functional and
barrier attributes. Various types of papers utilized in packaging food are discussed
below.
2.2.1. Kraft paper
This is produced using sulfate process, and is available in various forms such as
bleached-white natural-brown, unbleached, and heavy-duty. The strongest of them is
the natural-kraft and is usually utilized for wrapping and bags. The natural kraft
paper is also utilized in packaging dried fruits, flour, sugar, and vegetables. The
sulfite paper is usually weaker and lighter than kraft paper and glazed with the aim
of enhancing oil resistance, improving its appearance, and increasing its wetstrength. It is coated in order to attain higher quality of print and also utilized in
lamination using foil or plastic. It is utilized in producing small bags or wrappers for
packaging confectionaries.
2.2.2. Grease-proof paper
Grease-proof paper is produced through a beating process where cellulosic fibers go
through a prolonged duration of hydration which results in the fiber turning gelatinous
and eventually breaking [46]. Grease-proof paper is utilized in wrapping snack foods,
cookies, candy bars, and other greasily foods, though nowadays are being overtaken by
plastic films.
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2.2.3. Glassine
Glassine is a dense, highly smooth, and glossy paper utilized for biscuits liner, fast
foods, and baked goods [47].
2.2.4. Parchment paper
Parchment paper is derived from pulp which has gone through acidification process by
passing it through sulfuric acid. The cellulose undergoes acidification which makes it
smoother and not pervious to water and oil, thereby improving its wet strength. Its
deficiencies include poor air and moisture barrier, and lack of heat-sealability. It is
applied for packaging fats [48].
2.2.5. Paperboard
Paperboard is produced in multiple layers and is thicker than ordinary paper, with
superior weight per unit area. Paper board is utilized in producing shipping containers
including boxes, cartons, and trays, although it is scarcely utilized for close food
contact. Different types of paperboard include white board, solid board, chipboard,
fiber board, and paper laminate.
White board is produced from numerous thin-layering of chemical pulp which has
undergone bleaching; white board is usually used as a carton inner layering. In order to
ensure heat-sealability, white board may undergo coating using wax or lamination using
polyethylene (PE), and it is the major type of paperboard viable for direct food contact.
Solid board possesses strength and durability, and exhibits numerous layers of bleached
sulfate board. On lamination using PE, solid board is applied in creating liquid cartons
which is known as milk board. It is also applied in packaging soft drinks and fruit
juices.
Chipboard is produced using recycled paper. Nevertheless, it exhibits blemishes and
impurities from the base paper thereby making it not suitable for contact with food. In
some cases, it is lined with white board to enhance both strength and appearance.
Chipboard is the least costly type of paper board, and is applied in producing the
exterior layering of cartons utilized for foods such as beverages and cereals.
Fiber board exists either in solid or in corrugated form. The solid fiber board has an
internal white board layering and exterior kraft layering which enables adequate
protection against impactive and compressive forces. On lamination using aluminum
or plastics, solid fiber board enhances barrier properties and is utilized in packaging dry
products such as powdered milk or coffee. Corrugated solid fiber board also known as
corrugated board is produced using double layers of kraft-paper exhibiting a common
corrugating material. Fiber board’s resistance to impactive abrasion and crushing
damage makes it widely utilized in shipping bulk food and case packaging of small
food products.
Paper-laminates are usually coated or uncoated and fundamentally oriented on
sulfite and kraft pulp. In order to improve its properties, paper-laminates usually
undergo lamination using plastics or aluminum. For instance, paper can undergo
lamination using PE to ensure its heat-sealability and to enhance its moisture and gas
barrier properties. Though this factor increases the cost of paper. Laminated paper is
utilized in packaging dried products including herbs, soups, and spices [47].
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According to the reports of a research conducted by the Future of Global Packaging
to 2022, demand for packaging will steadily grow at 2.9% to attain $980 billion in 2022.
Another research by Smithers Pira forecasts a steady market growth of 3.1% till $11.40
billion in 2022. In 2016, the global carton board packaging market value attained the
$100 billion mark, while consuming more than 40.3 million tons of folding-carton
material and miniflute/micro-packaging applications. Thus, according to a research
forecast by the future of folding cartons to 2022, the global demand for carton board
utilized in folding-carton and micro-/miniflute packaging applications will increase at
4.0% Compound Annual Growth Rate (CAGR) to attain a market value of $124.1
billion by 2022 [47].
2.3. Metals
Packaging containers made of metals such as aluminum provide benefits such as
excellent heat dissipation and mechanical strength properties, elevated temperature
resistance, and impermeability to light and mass transfer. These attributes ensure that
packages composed of metals are specifically good in use for in-package heat
dissipation.
Aluminum used in packaging for instance does not require a protective coating
because of corrosion inhibition provided through the formation on the surface of the
material, a thin film of aluminum oxide which protects the metal from further corrosion. Due to the ductility and purity of some forms of Al, they are applied in
manufacturing foils and containers [49].
However, the two main forms of aluminum used in packaging are those used in
manufacturing cans used in beer and soft-beverages packaging and aluminum-foils
such as those used in manufacturing laminates [49]. According to the future of metal
packaging and coatings to 2023, the global metal packaging market experienced a
growth of 1.8% in 2015, attaining $102.9 billion, while in 2016, the global metal
packaging market grew by 3.1% to $106.1 billion, and expected to grow by 4.5% per
annum to a total value of $132.1 billion by 2023 (the future of metal packaging and
coatings to 2023) [50,51].
2.4. Metal films and laminates
The packaging lamination entails aluminum-foil binding to paper or plastic films to
enhance barrier properties. Though plastic lamination inculcates heat-sealability, the
seal scarcely hinders air and moisture [52]. Although, laminated aluminum is expensive relatively, it is usually applied in packaging dry foods such as spices, herbs, and
dried-soups.
Metallized-film is a more cost-effective alternative to laminated packaging. These are
plastics constituting of thin layers of aluminum metals. These films have enhanced
resistance to odors, oil, air, and moisture. Metallized films are more effective than
laminated films and are majorly utilized in packaging snacks. Although, single constituents of laminates and metalized films are recyclable, handicaps encountered in sorting
and separation of materials make recycling economically viable [52].
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2.5. Tinplate
This is fabricated using low-carbon steel or black plate. Tinplate is obtained from
coating both sides of black plate with thin layering of tin [53]. This coat is attained
through dipping of sheets of steel in molten tin or via tin electro-deposition on
electrolytic tinplates or steel sheets. Tinplate containers undergo lacquering in order
to provide an unreactive barrier between the metal and the food product.
Tinplate fundamentally is composed of low-carbon flat sheet of steel coated with
purified tin on both sides. Due to the escalating utilization of novel alternative materials
in the packaging industry, including aluminum, chromates steel sheet, and so on, still
tinplate is widely utilized in about 80% of the canning industry as a result of its
attractive appearance, effective corrosion resistance, and formability. However, remarkable challenges during utilization of tinplate cans in corrosive food products exist.
These issues include corrosion damages, seal-integrity loss, and problems associated
with discoloration. Moreover, researches have additionally revealed that high contents
of tin in food products may result in food safety issues. Nevertheless, despite its
products of corrosion neither involving toxic substances nor affecting flavor, very
high doses can result in critical digestive issues [54].
However, tin enables steel to hinder corrosion. Lacquers commonly applied include
materials such as vinyl-resins, epoxy, phenolics, and oleo-resinous groups. Tinplate
undergoes heat treatment and hermetic sealing, which makes it suitable for production
of sterile materials [55]. This is in addition to possession of excellent resistance to
odors, water vapor, gases, and light. Due to its ductility and formability, tinplate may be
utilized for containers of various shapes. Moreover, tinplate is versatily utilized in can
formation for drinks, aerosols, processed foods, and containers for food powders and
sugar/flour-oriented confectionaries and also packaging closures.
Tinplate is also effectively utilized as substrate for both metallic coating and lithographic printing, thereby facilitating efficient graphical decoration. Nevertheless, tinplate is easily recycled severally without quality loss, though it is significantly less
expensive when compared with aluminum. Its relatively poor weight and superior
mechanical properties easily facilitate its shipping and storing. Global tinplate consumption is forecasted to exhibit a robust growth represented by a CAGR of 5.68%
during 2018–2023 [56].
2.6. Tin-free steel
Tin-free steel is also recognized as chrome oxide-plated steel or electrolytic chromium.
In order to activate complete barrier to corrosion, tin-free steel is coated with an
organic substrate. Tin-free steel possesses reliable formability and strength; however,
it is less costly when compared with tinplate. Closures, food cans, can ends, trays, and
bottle caps are feasibly fabricated from tin-free steel. Additionally, it can also be utilized
in fabricating large containers such as drums for large-scale selling and also act as a
large bank of ingredients for finish goods [57]. Although the chrome oxide inculcates
unweldability to tin-free steel, the uniqueness of this attribute enables its effectiveness
for coating adhesion for inks, painting, and lacquers.
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For metallic cans, a major challenge is corrosion process which is very vital in food
packaging. This can be investigated both economically and hygienically. Food products
may undergo preservation in metallic cans for more than 2 years and devoid of any
significant variation in organoleptic attributes. A notable challenge is that cans are
prone to corrosion in comparison with other packaging materials [58].
3. Various forms of packaging
3.1. Intelligent/smart packaging
Intelligent and smart food contact materials are majorly tailored to be used in monitoring the freshness of packaged food, in addition to the environmental condition surrounding the food. This system has the capability of providing information to the
consumer or supplier via a visible indicator that provides information regarding the
level of freshness of the foodstuffs, or if the packaging underwent damaging, breaching,
or maintained at the appropriate temperature across the supply chain.
The main parameters affecting their broad application include propensity to be
compatible with varying packaging materials, cost, and robustness [59]. The date of
food to expire is determined by industries through consideration of the peculiar
arrangement and conditions of storage especially the temperature at which the food
item is probably going to face. Unfortunately, it is established that such conditions are
not always the actual conditions of exposure and the temperature at which food is
exposed is quite erratic, especially for food requiring cold chaining.
Initially, evolvements were rooted on instruments which were inculcated within the
food item in an acceptable packaging with the objectives of monitoring the integrity of
the package and the time–temperature record of the food item, in addition to determination of the actual expiration date.
Suppliers were enabled to checkmate the actual temperature of maintenance of the
food item using time–temperature indicators (TTIs) which appeared on some food
items in the late twentieth century [60]. These TTIs were separated into two classes. The
first class depended on dye transport via a porous material as a function of time and
temperature, while the other depended on a chemical reaction which commenced when
the food label was placed on the packaging, ending in a variation of color [61]. These
parameters enabled customers to ensure the product they were buying and facilitated
manufacturer’s ability to track foods across the supply chain. However, the capability of
checkmating food across the supply chain enabled manufacturers’ identification and
redressing of the malfunctioning sections.
However, defects in the packaging arrangement such as micro-holes and sealing
faults can result in unprecedented exposure of the food item to oxygen which can have
negative effects on the food product. Nevertheless, information regarding the package
condition can be obtained through the use of NPs which can act as reactive particle in
the packaging material. These nano-sensors possess the capability of responding to
environmental variations such as humidity, degree of exposure to oxygen in storage
rooms, temperature, and levels of product deterioration or microbial degradation [62].
The inculcation of nano-sensors in food packaging facilitates depiction of some toxic
and pathogenic chemicals in food, in addition to enabling effective detection and
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elimination of false expiration dates while revealing the actual food condition [63].
Thus, recent emerging trends in smart food packaging involve the use of pathogen
sensors, oxygen, and freshness indicating apparatuses. The presence of oxygen enables
the development of aerobic microorganisms on stored food.
Moreover, recently, there has been the evolvement of pH indicators based on organic
nSiO2 [63]. This freshness indicating devices regulate packed food quality by reacting to
variations occurring in fresh food products due to the development of microbes. The
knowledge of quality-indicating metabolites is a very important factor in the manufacture of freshness indicating apparatuses used in detecting degree of food freshness [64].
There has been an escalating interest in development of nontoxic and irreversible
oxygen sensors which facilitates assurances of zero oxygen levels in oxygen-free food
packaging systems, such as packaging in vacuum or in the presence of nitrogen. Thus, a
nanocrystalline SnO2 has been used as a photosensitizer in a colorimetric oxygen
indicator based on the principle of variation in film color as a function of oxygen
exposure. Also recently, an ultraviolet-based colorimetric oxygen indicator using TiO2
NPs in photosensitizing the miniaturization of methylene-blue (MB) using tri-ethanolamine in a polymer encapsulating system via UVA light was produced. The sensor
undergoes bleaching and maintains a colorless state when UV-irradiated, but on
exposure to oxygen, it returns to its original blue color. Here, it was ascertained that
the extent of color recovery is equivalent to the degree of exposure to oxygen. This
freshness indicating apparatuses must contain a metabolites sensitive sensor capable of
reacting to a metabolites environment with the necessary sensitivity [2]. A microbial
environment capable of degenerating food quality is picked up by an indicator system
through a variation in color. The packaging type and the natural attributes of the
packed food product degeneration flora determine the development of the various types
of metabolites. However, the sensors inputted on the packaging films must exhibit
capability of detecting food degenerating microbes and induce a color variation to
notify the customer that the product is expired or nearing expiration [2].
Numerous investigations have shown that inclusion of antimicrobial agents in the
packaging films may efficiently minimize development of food degenerating microbes
in packaged food thereby enhancing food preservation [65]. In a bid to meet up to
consumer expectations toward a more natural, biodegradable, recyclable, and disposable food packaging material, studies have been directed toward inclusion of naturally
occurring antimicrobial additives such as plant extracts and bacteriocins into the biobased packaging material instead of plastic films [66].
Nowadays, coatings and consumable films have aroused increasing interests among
materials used for packaging fresh poultry and meat as a result of numerous accruable
benefits [67]. Consumable films and coatings make up a significant class of bio-based
packaging material. Consumable coatings are applied directly on food products either
via liquid films producing solution or molten substances or through traditional plastic
processing methods [68]. Consumable films and coatings facilitate resistance toward
carbon dioxide (CO2), oxygen (O2), and moisture. Factors critically imperative in
effective packaging include safety considerations, food quality, losses reduction, and
environmental friendliness. Food packaging plays vital roles in food distribution,
storage from farm to dinning table, while also contributing to waste generation [69].
Nowadays, the objective of food packaging systems is based on the prospective ability of
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prolonging shelf life of perishable foods, through reduction of preservatives and additives requirement, while considering quality variations. Food is versatily classified into
passive, active, intelligent, and smart packaging [68].
Smart packaging is based on utilization of electrical or electronic, chemicals or
mechanical techniques, or any combinations of them [70]. Specifically, smart packaging
includes technology utilization which adds features which ensure packaging becomes a
permanent component of the whole product [71]. Nowadays, interests at utilization of
active and intelligent packaging systems for agricultural fresh products have escalated
[72]. Active packaging (AP) refers to the incorporation of additives into packaging
systems, with the aim of maintaining or extending the shelf life and quality of fresh
vegetable or livestock products, while intelligent packagings are those systems capable
of monitoring the condition of packaged foods in order to provide information with
regard the quality of the packaged food during transport and storage. Apart from the
development of intelligent packaging system through use of sensor technology, indicators such as TTIs, freshness, integrity, and radio frequency identification have undergone evaluation for prospective utilization in meat and by-products [71,72].
Active and smart packaging conducts more functions in addition to the basic ones
and can be backed up by intelligent packaging systems. Intelligent packaging involves
the introduction of novelty in packaging design, including other conveniences for
the user and usefulness for the consumer or firms involved in the supply chain. Thus,
the product can respond to externally generated stimuli from the environment or from
the product undergoing packaging.
Very recently, interest in utilization of active and intelligent packaging systems for
meat and its by-products has escalated. AP reveals the inclusion of additives into
packaging systems with the objectives of maintaining or prolonging the quality and
shelf life of meat products. Commonly known AP systems include CO2 scavengers and
emitters, oxygen scavengers, moisture controlling agents, and antimicrobial packaging
technologies. Intelligent packaging involves monitoring the condition of packaged
foods in order to offer information with regard to the quality of the packaged food
during transport and storage [73].
Active and intelligent packaging involves purposeful interaction of packaging with
food and its immediate environment aimed at improving food quality and safety. This
includes technologies such as advancement in slowed oxidation and monitored respiration rate, growth of microbes, and moisture migration. Other instances include CO2
absorbers/emitters, odor absorbing agents, ethylene eliminators, and aroma emitting
agents, while intelligent packaging includes time–temperature and ripeness indicators,
radio frequency identificators, and biosensors [2]. Nevertheless, as a result of its specific
interaction with food and its environment, substance migration is a food safety challenge. Hence, intelligent packaging is an emerging technology utilizing communication
attribute of packaging to enable decision-making in order to attain advantages of
enhanced food quality and safety. Recent advances in smart packaging tools include
biosensors, barcode labeling, radio frequency identificators, time–temperature, and gas
indicating devices.
AP entails the interactions between food, packaging materials, and the atmosphere.
Utilization of oxygen scavenging systems is effective in reducing the degree of residual
oxygen dissolved or abiding in the head-space far lower than those attained through
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modified atmosphere packaging (MAP) technologies. CO2 scavengers are efficient at
controlling fruits/vegetables post-harvest respiration, inhibiting oxidation of flavor in
ground-coffee while controlling the development of aerobic and anaerobic microorganisms [71–73].
3.2. Active packaging
Presently, AP evolved majorly for use in antimicrobial packaging. It is fashioned to
inculcate agents capable of releasing or absorbing substances via the environment
around the food or the packaged food itself [74]. Potential applications of AP include
scavenging for oxygen, extraction of ethylene, and CO2 absorption and emission.
Recently, numerous researches have been conducted on the use of NPs as active
reinforcement in polymeric nanocomposites used in food packaging applications [75].
A recent study reported that carvone-filled low-density polyethylene (LDPE) films
applied in AP facilitated the effect of supercritical CO2 induced impregnation on
loading, mechanical and transport properties of the films [75]. AP is a material that
varies the packaging condition to prolong the shelf life of the material while also
improving the quality, safety, and sensory properties of the food.
Antimicrobial packaging being one of the innovative AP techniques, utilizing antimicrobial agents in food packaging materials, has received wide acclamation as a
prospective use for a broad range of foods such as meat, fish, poultry, bread, cheese,
fruits, and vegetables [76]. Prospective use of these films exhibiting antimicrobial
activities enables surface contact with food thereby controlling growth of pathogenic
and food deteriorating microorganisms. The most commonly used NPs in developing
antimicrobial AP PNC include CNTs, metal NPs, and metal oxide nano-materials [77].
The most investigated metallic NPs possessing antimicrobial capabilities and utilized
in numerous commercial areas are zinc, gold, and silver nanoparticles (AgNPs). These
NPs operate by directly contacting the organics abounding in the substrate, though they
also exhibit gradual migration with preferential interaction with microbes exiting in the
food substrate. AgNPs, exhibiting less volatility and stability at elevated temperature,
have revealed efficiency against about 150 types of bacteria with antifungal and microbial effectiveness [8,77].
The mechanical and antibacterial attributes of nanocomposite films of CMC/OM/
ZnO NPs have been successfully attained. The tensile property of the film was enhanced
by the NPs . Okra mucilage induced more color into the films. Inclusion of okra
mucilage and ZnO NPs enhanced antibacterial attributes [78].
In a study, AgNPs were employed as bactericidal agents and were introduced in a
matrix of hydroxyl-propyl-methylcellulose (HPMC) utilized as packaging materials for
food substrates. Properties exhibited by HPMC-AgNPs nanocomposites films include
good barrier and mechanical properties. Results revealed that presence of AgNPs in
HPMC matrix improved the tensile strength of the films. Overall, results revealed that
the nanocomposites could behave as active antimicrobial internal coatings when utilized in food packaging [79].
Various types of mechanisms have been elucidated to expatiate the antimicrobial
attributes of AgNPs such as bonding to the surface of the cell, invasion of the interior of
the cell of the bacteria, degradation of lipo-polysaccharides and formation of holes
COMPOSITE INTERFACES
13
inside the membranes, bacteria-DNA degradation, and emission of ions which bonds to
groups donating electrons in molecules containing oxygen, Sulphur, or nitrogen [80].
Several researchers have obtained silver nanocomposites exhibiting good antimicrobial efficiency [77–80]. An investigation has revealed the superiority of silver nanocomposites in comparison with silver microcomposites [81].
In situ polymerization was utilized in the production of PE nanocomposites composed of AgNPs exhibiting antimicrobial attributes [82]. These PE-AgNps nanocomposites were found to be effective against Escherichia coli as functions of the quantity of
AgNPs incorporated and the duration of contact. Transmission electron micrograph
(TEM) studies revealed that there was good dispersion of AgNPs thought to be caused
by the use of oleic acid as modifying agent thereby improving the surface adhesion
between PE and the NPs. The quantity of silver ions emitted from the nanocomposites
revealed the antimicrobial attributes of PE-AgNps nanocomposites. Studies revealed
that nanocomposites composed of 5 wt% AgNps exhibited elevated silver ion emission
and post 24 h exposure destroyed 99.99% of the microbacteria existing in the environment thereby displaying excellent formidability against bacteria in comparison with
pristine PE. Thus, results revealed formation of an excellent antimicrobial substrate.
The biosynthesis of AgNPs and polyhydroxybutyrate nanocomposites for antimicrobial applications has been investigated [83]. This research investigated the optimization
and improved production of poly-3-hydroxybutyrate nanocomposites composed of biosynthesized AgNPs used in generation of highly effective antimicrobial materials. These
studies revealed the feasibility of Cupriavidus necator to minimize silver salt production
while releasing AgNPs without inclusion of a reducing agent in addition to the
influence of the route of synthesis (with or without reducing agent) in the distribution
of AgNPs and their antimicrobial performance which enhances their potential suitability for use in active coatings and packaging [84].
In another study, the inclusion of nanocrystals of zinc in polymer matrix resulted in
formation of effective antifungal, antimicrobial, and antibiotic agent [85]. Also, oxides
of NPs have been applied as disinfectants, ultraviolet blockers, and photocatalytic agents
such as magnesium oxide, ZnO, TiO2, and silicon oxide (SiO2) [85].
For decades, these NPs have been applied in sun creams as white pigments for
printing inks, paints, paper, and plastics. TiO2 has been investigated for use as photocatalytic disinfectants for surface coatings in packaging materials (Kong et al. 2010).
Research has revealed that TiO2 photocatalysis enhances peroxidation of polyunsaturated phospholipids and fatty acid of microbial cell membranes [86], and also used in
the inactivation of numerous pathogenic bacteria in food substrates [87].
Powder-coated packaging films based on titanium oxide have been developed and
results revealed efficiency against fecal coliforms existing in water, and contamination
of food substrates by E. coli [88]. Doping of metals has been found to enhance the
absorption of visible light and bacterial photocatalytic inactivation under ultraviolet
irradiation of TiO2 [89,90].
CNTs apart from enhancing the attributes of polymer matrix have also exhibited
antibacterial propensities. NPs of CNTs have been shown to kill E. coli on close interaction and this has been attributed to the propensity to break the cells of the microbes by
the thin and lengthy structure of CNTs resulting in destructive damages [91,92].
Presently, versatile application of CNT is strictly limited as numerous investigations
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C. I. IDUMAH ET AL.
have revealed the cytotoxicity of CNTs to human cells, especially on close interaction with
the skin [93].
Food spoilage can also occur through the presence of oxygen in a package which
initiates or propagates oxidative reactions which induce food spoilage by facilitating the
development of aerobic microorganisms. Moreover, side effects of oxidative reactions
(direct and indirect) include negative color variations, off-odors, minimized nutritional
quality, and off-flavors. The scavenging by oxygen eliminates oxygen both residual and/
or penetrating which in turn retrogresses oxidative reactions. Thus various types of NPs
such as titanium oxide have been employed in the production of oxygen scavenger
films. Also, AgNPs exhibiting antimicrobial activities have shown affinity in absorption
and decomposition of ethylene. Ripening products of natural plants emit ethylene as
hormone. Thus, the elimination of ethylene from a package ensures extension of the
shelf life of fresh farm products such as vegetables and fruits.
AP includes methods in connection with substances capable of oxygen absorption,
flavors/odors, moisture, CO2, ethylene, and others capable of releasing antimicrobial
agents, antioxidants, CO2, and flavor [94]. AP has capability of removing unwanted
flavor and tastes while improving the smell or color of the packaged food. These types
of materials undergo interaction with packaged food and the environment enveloping
the food while playing active functions such as shelf life extension, sensory or safety
properties enhancement, while maintaining quality of packaged food. This packaging
technique has undergone modification aimed at providing sustainable quality, food
safety, and reduction of package-based environmental deterioration and disposal
issues [95].
3.2.1. Oxygen barrier/oxygen scavenging
Oxygen presence in packaged foods results in numerous challenges such as off-flavor
issues, color variations, loss of nutrients, and microbial growth [30]. Moreover, it also
significantly influences production of ethylene and the rate of respiration in fruits and
vegetables. Despite packaging oxygen-sensitive food with passive barrier packaging
films such as superior barrier packaging films composed of multilayered structures
[96], or barrier nanocomposite [97], the passive technique does not entirely eliminate
the oxygen. Thus, dissolution of oxygen may occur in the food, remain in some parts or
permeate into the walls of the container. In order to overcome such challenges, an AP
technique utilizing oxygen scavenging systems has been prepared to minimize oxygen
residues remaining in the package; however, high adverse prospects of anaerobicpathogenic bacterial development exist.
Oxygen scavenger can be utilized in small sealed sachets which are input into the
package or fixed via adhesion to the interior walls of the packaging films. There are
challenges facing this technology such as incidental ingestion of the sachets contents
and the problems of recycling. Application of PNC could offer solution to these issues.
Ascorbic acid-oriented oxygen scavenger has been developed for active food packaging
system for raw meat-loaf [96]. And proteomic analysis has been conducted to investigate color variations of chilled beef longissimus steaks held under carbon monoxide and
high oxygen packaging [98]. Recently, the development of active food packaging
material via supercritical impregnation of thymol in poly(lactic acid) (PLA)-reinforced
electrospun poly(vinyl alcohol) (PVA)-cellulose nanocrystals (CNC) nanofibers has
COMPOSITE INTERFACES
15
been conducted. The deterioration of numerous types of food is a result of either direct
or indirect oxygen reactions. For instance, the decoloration of fruits and vegetable oil
rancidity is caused by direct oxidation reactions. The spoilage of food by indirect
oxygen interactions includes food deterioration by aerobic microorganisms.
The level of oxygen in food package films can be lowered through inclusion of O2
scavengers into food packages. This is useful in numerous applications. Films made of
oxygen scavengers have been developed successfully through inclusion of titania NPs to
various polymers. The prospects of using these nanomaterials in packaging a broad
range of products which are oxygen sensitive were suggested by the authors. However,
TiO2 operates via photocatalytic mechanism, and its main deficiency is UVA light
requirement. However, recent interests have been focused on the photocatalytic
mechanism of nanocrystals of titania (TiO2) under ultraviolet radiation [99].
Recently, safe eating and healthy food insight among consumers is escalating. Foods
which are sensitive to oxygen can be better protected utilizing oxygen scavenging films,
an emerging technology prolonging the shelf life of food products while also maintaining the quality and freshness of the food products. Utilization of oxygen-absorbing
materials in packaging is a current trend in AP, especially in food packaging. Some
oxygen scavenging films have shown excellent oxygen absorption while becoming
commercially successful [100].
3.2.2. CO2 emitting and absorbing mechanism
In a bit to hinder development of surface microbes and also prolong the shelf life of foods
such as meat and poultry, a high concentration of CO2 in range of about 10–80% is
imperative. Oxygen elimination from the package partially forms a vacuum which collapses
the flexible package. Thus, the automatic release of oxygen consuming CO2 from inserted
sachets is imperative. This type of mechanism has been developed via ferrous carbonate or a
combination of sodium bicarbonate and ascorbic acid [100]. In order to enhance elimination of CO2 during storage and hinder package breakage, calcium hydroxide, potassium
hydroxide, sodium hydroxide, calcium oxide, and silica gel have been utilized in CO2
absorber sachets. A versatily utilized CO2 scavenger is calcium hydroxide which undergoes
reaction with CO2 at high moisture content to form calcium carbonate. However, the flaw
in utilizing calcium hydroxide is in the irreversible scavenging of CO2 which results in
depletion from the package and this is unrequired [98].
The capability of films having an active layer of nanoporous crystalline syndiotactic
polystyrene (s-PS) to extend the shelf-life of both climacteric and non-climacteric fruits
has been investigated [101]. Studies on oxygen and CO2 concentrations in the environment of packaged fruits as well as in s-PS active layers reported that extended shelf life
is associated with high improvement of CO2 concentrations and reduction in oxygen
concentration inside the packaging film. Data derived are consistent with higher barrier
offered to both gases by nanoporous–crystalline s-PS layers [102]. This barrier activity is
attributed to gas diffusivity of nanoporous–crystalline polymer films, which is further
effected by orientation.
3.2.3. Ethylene eliminators
Ethylene is a plant ripening hormone which has physiological influence on vegetables
and fresh fruits. Ethylene effects on plants result in yellowing discoloration of green
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C. I. IDUMAH ET AL.
vegetables and are the cause of various postharvest faults in plants. It propagates the
rate of respiration, resulting in softening, maturity, and ripening of fruits in addition to
senescence. In order to prolong the shelf life and quality of packaged food, the
accumulation of ethylene in packaged food should be eliminated. A novel approach
bioactive packaging plays a vital role at improving the consumer’s health [63]. Ethylene
(C2H4) regulates plant growth. It is a plant growth stimulating hormone propagating
ripening degree and senescence through increase of their rate of respiration. Moreover,
it increases the rate of chlorophyll degradation, especially in leafy products, and
stimulates rapid softening of fruits [62]. Due to these challenges, ethylene elimination
from the product environment through inclusion of ethylene scavengers’ delays ripening and senescence, thereby improving quality and extending product shelf life.
Due to their nutritional and health enhancing inputs, fruit and vegetables are required by
consumers. However, various factors influence the postharvest existence of these products
such as humidity and temperature and especially ethylene, which even at low concentrations
plays a major role. Hence, growing interests have focused on the development of efficient
tools to eliminate ethylene from the environment surrounding these products during storage
or during transport. Nevertheless, potassium permanganate (KMnO4) scrubbers are major
technologies utilized in eliminating ethylene from horticultural products. In order to enable
and enhance the oxidation process, KMnO4 has been placed on top of inert solid substrates of
small particle sizes. The commonly utilized materials include nanoclay, activated alumina,
silica gel, vermiculite, and zeolite. Literature has suggested that KMnO4 placed on top of silica
gel or zeolite portrayed a potential tool in maintaining fruit and vegetables quality properties
for prolonged storage [30].
KMnO4 is a notable ethylene scavenging system composed of either the incorporation of a small sachet containing a specific scavenger in the packaging or inclusion of an
ethylene absorber in the film package. Usually, the included sachet substrate is highly
permeable to ethylene, and enables diffusion through it. KMnO4 is the most common
active component of the sachet in order to enable the oxidization and inactivation of
ethylene [103]. Nevertheless, KMnO4 is usually not utilized in direct food contact as a
result of its high toxicity.
Chitosan has been utilized for AP of ethylene absorber capable of changing the head
space of food packaging to prolong shelf life. The significance of this study was
development of AP from chitosan and KMnO4 and its application to active film
packaging of tomatoes [103]. However, the food industry has experienced serious
pressure to feed a rapidly increasing world population and expected to adhere strictly
to enacted food safety law and regulation. Moreover, active carbon, zeolite, and pumice
are ethylene scavenging systems which are based on utilization of finely distributed
minerals. Aforementioned minerals could be included in plastic film structures utilized
in packaging of fresh produce. The intention is for these minerals to scavenge ethylene,
in addition to the modification of the film gas permeability so as to enable rapid
diffusion of CO2 through pure PE in order to derive an equal atmosphere.
Other notable ethylene eliminators are metals and metallic oxides. Ethylene has been
oxidized into water and CO2 by photoactive TiO2. On the other hand, since metallic
oxides undergo activation by either visible or UV light, or both, the adverse effects of
UV light on quality of food should be given precautionary consideration. Ethylene
scavengers have the capability of extending the shelf life of climacteric fruits and
COMPOSITE INTERFACES
17
vegetables [75]. The underlying principle for effective packaging of fresh-cut produce is
gas equilibrium in the headspace such that the oxygen and CO2 permeability of the
packaging film and the degree of respiration of the produce should be equal. This is in
addition to elimination of ethylene from the packaging environment.
The inclusion of oxygen and low CO2-MAP in conjunction with ethylene eliminator
could potentially offer added advantages to enable adequate controlling of the product
of metabolism while also increasing the shelf life of fruits and vegetables in comparison
with MAP application. Nevertheless, the packaging parameters should notably be
designed to be produce-specific, since individual produce changes with degree of
respiration, rate of ethylene production, and the sensitivity of ethylene. Thus, these
factors result in variation of the requirements for packaging and storage [104].
3.2.4. Moisture scavengers
Increasing moisture content results in food products being highly prone to microbial
deterioration and potentially result in changes in appearance and texture, and subsequently minimize shelf life. Thus, the content of moisture and activities of water are
critical factors influencing the quality and safety of different types of foods [83].
Techniques of moisture control in packaging are classified into two categories. This
refers to moisture reduction, for instance, by MAP through replacement of the humid
air in the headspace by dry MA gas, or via vacuum packaging (VP) through elimination
of humid air in the headspace, inhibiting moisture via barrier packaging, and moisture
removal through the application of a desiccant/absorber. From the aforementioned
categories, the latter category only may be taken as active, while moisture minimization
and inhibition are considered passive systems.
Passive strategies may include those systems with potential of reducing the humidity
devoid of any active materials, such as micro-perforated films. For instance, materials
such as Xtend-R films produced in Tefen, Israel. The level of humidity accruable inside
packaging substrates can be controlled by carefully selecting packaging materials exhibiting high resistance to water vapor [105]. Thus, active moisture scavengers can further
be distinguished into two major types such as relative humidity (RH) controllers which
scavenge humidity in the head-space including desiccants, and moisture eliminators
capable of liquid absorption [106]. The latter has potential application in form of pads,
sheets, or blankets, which are commonly positioned under fresh products in varying
packaging perspective such as vacuum, skin-pack, MAP, and so on. These are especially
utilized for cut food products expressing high water activity such as fruits, vegetables,
fish, meat, and poultry [107]. Thus, drip-loss escalates relative to storage duration and
by increasing the exposed surface area, and longitudinally cutting-off muscle fibers.
These types of pads are usually comprised of materials that are porous such as polymers
including PP or PE, polystyrene (PS) foamed and perforated-sheets, or cellulose in
combination with super-absorbent polymers or minerals or salts such as polyacrylate
salts, carboxymethyl cellulose, starch copolymers, and silica or silicates [108].
Notably, during storage, numerous dry products are sensitive to humidity. Moreover,
poor levels of RH in the interior of the packages may result in significant deterioration
of product quality. However, for some products such as meat, fruit, vegetables, and
fresh fish, maintaining a controllably high level of RH in the package interior is
advantageous in hindering drying. Additionally, drip-loss resulting from some excess
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C. I. IDUMAH ET AL.
moisture is common for some fresh products such as fish and meat. Thus, consumers
understanding of moisture in a package are that of minimizing the product attractiveness which lowers the product desirability [109].
Pads exhibiting moisture absorption are not regularly considered as AP materials.
Materials and articles such as pads operating on the basis of inherently natural
components only, and containing 100% cellulose, are not categorized as active materials. This is as result of the fact that they are not deliberately designed to include
constituents capable of releasing or absorbing substances. Nevertheless, moisture
absorbing pads containing components which are intentionally fabricated to enable
moisture absorption from food may be considered as AP materials. Hence, absorption
pads may be utilized in conjunction with antimicrobial agents, pH monitoring agents,
and/or CO2 generating agents, in order to eliminate certain deficiencies, such as odor
emission or leakages. Desiccants such as clays, silica gel, zeolites, and so on are utilized
in controlling humidity in the packaging headspace. The desiccants absorption capacity
depends on its water vapor sorption isotherm and commonly positioned in packages in
the form of microporous bags, sachets, or integrated into pads.
3.3. Vacuum packaging
VP ensures the prevention of oxidative reactions such as pigmentation and vitamins
loss, oxidation of lipids, browning induced by oxidation, and so on. Additionally, it
ensures prevention of deterioration caused by aerobic microorganisms especially mold.
VP is an established and popular method, utilized in the packaging of various types of
products [110]. It provides other benefits such as reduction in volume and improvement of flexible packaging rigidity [111]. It also enables extension of the shelf life of
refrigerated fresh poultry and meat [112–114].
VP assists in compressing package against food products in retortable pouches
thereby improving thermal conductivity. Apparatuses utilized in pulling vacuum in
package prior to sealing for pouches, jars, cans, and trays are available [115].
Skin packaging, a novel technique in meat packaging, is the most newly emerging
packaging technique utilized for storing meat [116]. Here, raw meat is positioned on a
plastic tray, and covered using a plastic thermoformed film concurrently with time of
meat apposition, therefore acquiring a replica shape of the piece of meat. The specific
top-skin shrinking via heating in vacuum-skin packaging secludes air formation which
eventually results in visible exudate formation and efficient prolonging of the microbial
shelf life. The extreme plastic film adherence to the surface of product eventually results
in improvement of all sensorial attributes of the prospective consumer.
3.3.1. Rigid, biodegradable, and flexible packaging materials
The fundamental hindering factors for the shelf life of various foods and beverages shelf
life are the packaging materials restriction to gas invasion such as oxygen and water
vapor and gasses retention such as CO2 and aroma [117].
A study has focused on identification of a technique, offering antibacterial resistance
to a thin film of zein. Singly separated and spindle-like ZnO crystals composed of
nanocrystals were synthesized and included into the films. Energy dispersive X-ray
(EDX) mapping results affirmed the uniform dispersion of ZnO in films. The
COMPOSITE INTERFACES
19
antibacterial propensity of the film was attained and revealed great stability. Thus, the
prospects of zein thin films including ZnO crystals as functional packaging film were
revealed [118]. Figure 3(a) reveals an analysis of the inorganic part and zein morphologies of conjugated ZnO crystals (a) XRD spectrum; (b) scanning electron microscopy
(SEM) observation; (c–e) TEM observation. Figure 4 elucidates morphological images,
elemental constitution, and phase dispersive detection of zein thin films.
Thus, ZnO crystals revealed durable and prolonged antibacterial action toward both
Gram-negative and Gram-positive pathogens. However, the bacteriostatic effect was
ascribed to the release of zinc ion from the thin film.
The mobility of CO2 from carbonated beverage bottles could minimize the shelf life
by flattening the beverage. However, the migration of oxygen into beer bottles interacts
with the beer thereby making it stale. A proffered solution to both challenges is provision
of a barrier to the molecules mobility through the polymer matrix. PNC comprising of
various nanofillers have undergone development for enhanced gas and water vapor
barrier attributes [119]. Elucidated classification of PNC is given in Figure 5.
Multilayered PNC for rigid food packaging are the packaging materials used for
carbonated beverages, bottling beer, and thermo-formed containers [120]. The basic
food packaging materials possessing multilayer structures include food packaging
materials consisting of single polymer which pose as barrier to molecules of gas or
water vapor. The other type is termed passive barrier. In passive barrier, the middle
layering undergoes reinforcement using a nanocomposite film with improved barrier
attributes [121]. Another type is an active barrier packaging material consisting of an
oxygen scavenger included in the polymer [122,123]. There is another type consisting of
the combination of passive and active barriers [124].
Figure 3. Analysis of the inorganic part and morphologies of zein-conjugated ZnO crystals. (a) XRD
spectrum; (b) SEM observation; (c–e) TEM observation; (f–g) analysis of zein composition in
conjugated ZnO crystals via TG/DTA. Zein-conjugated ZnO crystals and pristine zein (blue color)
[118].
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C. I. IDUMAH ET AL.
Figure 4. Morphological images, elemental constitution, and phase dispersive detection of zein thin
films with crystals inclusion. (a) Visual image; (b) SEM image-facade; (c) SEM image-profile; (d) EDX
analysis; (e) EDX mapping on N; (f) EDX mapping on Zn; the antibacterial activity of zein-conjugated
ZnO crystals with varying concentrations against (g) S. aureus and (h) E. coli using the disc diffusion
technique. The antibacterial activity of a thin film of zein with inclusion of ZnO crystals after dipping
in an aqueous solution at various times. (i) S. aureus and (j) E. coli [236].
Figure 5. Elucidative classification of polymer nanocomposites.
COMPOSITE INTERFACES
21
In biodegradable packaging films, biopolymers are utilized in the fabrication of
varying types of biodegradable food packaging films. The materials water vapor barrier
attributes have been enhanced utilizing nanofillers from renewable resource.
Flexible packaging materials include materials made from films, foil, or paper
sheeting including wraps, envelopes, bags, pouches, and sachets which acquire a pliable
shape on filling and sealing. Packaging films made with metallic layering escalate the
solid waste amount in the environment post-disposal. Nowadays, numerous packaging
materials are multilayered and are unrecyclable. Nevertheless, PNC could facilitate
reduction in packaging waste thereby enabling recycling. The main objective of utilizing
PNC includes moderation of the quantity of solid waste emanating from the present
packaging system in addition to costs reduction through material economy. Potential
applications of PNC packaging materials are shown in Figure 6.
A VP global market forecast to 2023 for PE, and polyamide (PA) packaging (rigid
packaging, flexible packaging, and semirigid packaging), has been presented by Market
research future (MRFR; 2017). VP is a form of MAP. VP eliminates atmospheric oxygen
from the package to undergo sealing since the presence of oxygen is one major cause of
food product spoilage. Thus, oxygen elimination prolongs the shelf life of the product. VP is
usually utilized in the protection of consumable and nonconsumable products. The VP
market share is determined by factors such as increasing beverages and processed food
consumption, rapid urbanization, industrialization, and increased government policies
Figure 6. Attributes and prospective applications of polymer nanocomposite in food packaging.
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C. I. IDUMAH ET AL.
regarding food safety while its limiting factors include stringent regulations on packaging
materials waste disposing and recycling. The major consumption market group for packaging materials and machineries is the food and beverages sector. The global VP market is
militated by varying parameters expanding urbanization, improved standards of living, and
growing disposable income in emerging economies.
The food and beverages sector has majorly dominated the VP globally as a result of
some vital functions such as product integrity retention, and prevention of food
spoilage, in addition to the prolonged shelf life. These factors encourage the retail
outlets where fresh and processed food products are warehoused over long duration of
time, while simultaneously encouraging consumer permission in viewing and feeling
the product from the packaging. These parameters power the interests for VP in the
foods and beverages sector.
In the foregoing report, the global market for VP is segmented into material, packaging, and application. PE and polyamide (PA) packaging films are the basis of the
material market segmentation. With regard to value in 2016, the PE market segment
dominated the global VP market with 49.23% share. The PE market share is expected to
demonstrate the greatest growth at a CAGR of 5.10% during the duration of forecast.
This domineering position of PE can be ascribed to the progressive utilization of PE
across all end application. Based on this premise, this market is further segmented into
rigid, flexible, and semirigid packaging. In terms of value in the year 2016, the flexible
packaging sector domineered the global VP market with 42.56%. The market is projected
to grow at a CAGR of 5.39% during the duration of the forecast. Relative to value in 2016,
the food packaging segment dominated the global VP market with 31.69% share. The
flexible packaging market share is forecasted to grow at a CAGR of 5.16% during the
duration of the forecast.
3.4. Modified atmosphere packaging
The major functions of food packaging include protection of food substrates from external
effects and damage, food containment and providing consumers with nutrient and ingredients information [125]. The objective of food packaging also involve cost efficient containment of food in order to satisfy industrial requirements and consumer expectations, food
safety adherence, and reduction of hazardous environmental influences [126].
MAP of food product defines the methods utilized in packaging actively breathing
food products in polymer-based film packages to enable modification of the degrees of
O2 and CO2 surrounding the packaging atmosphere. The generation of low O2 and high
CO2 atmosphere is imperative at enabling metabolism of food product under packaging
and the level of deterioration inducing organism activities so as to improve food
storability and/or shelf life [127–132].
Generally, MAP enables improvement in retention of moisture thereby influencing
quality preservation than O2 and CO2 levels while also modifying the atmosphere.
Additionally, packaging separates the food product from externally impacting environmental factors while assisting in ensuring potent conditions or minimization of exposure to pathogens and contaminating entities. Moreover, MAP of food products
depends on atmospheric modification of the package interior attained via the naturally
occurring interaction between the rate of commodity respiration and the packaging
COMPOSITE INTERFACES
23
films degree of permeability. MAP has demonstrated an assured technology in satisfying consumer’s escalating quest for a more naturally available fresh foods [133–135].
The marketing and distribution requirements of a product determine the type of
packaging design. Packaging attributes include product protection from mechanical
damage, elimination of moisture loss, and modification of the internal atmosphere to
prolong product shelf life [136–139]. Physical damages such as vibration and compression crevices or aberrational damages can undergo reduction through proper package
designing facilitating shock absorption.
Moreover, packages enable products to rapidly attain optimal storage temperature.
MAP is a technology altering the atmosphere enclosing the package in accordance with
the interaction between the product rate of respiration and the gaseous transfer through
the package [140–143]. Here, the food product undergoes packaging in an atmosphere
comprising of gaseous mixture depending on the packaging material, product, storage
conditions, and anticipated product shelf life [144–147].
Thus, subsequent variations in packaging atmosphere normally depend on the
breathing mode of the packaged food, the availability of atmospheric modifiers, and
the specific packaging material permeability. Recently, the influence of MAP and
antimicrobial edible coatings packaging on the microbiological status of cold stored
hake (Merluccius merluccius) fillets has been successfully conducted [145]. Results of the
effect of the combinations of lipid, storage temperature, and modified atmospheric gas
on CO2 solubility in a seafood model product revealed MAP efficiency at food preservation [146].
MAP is also utilized for food products that are perishable and also susceptible to
chemical changes like coffee. Thus, perishable food items including fresh fruits, vegetables, fish, and meat products are preserved in refrigeration with flexible films. Thus,
food products undergoing marketing under the auspices of MAP include meat, poultry,
dairy and bakery products, vegetables, fruits, and fish [148–151]. The accruable benefits
from MAP are mostly ascribed to development and maintenance of an atmosphere
devoid of oxygen. Nevertheless, this is dangerous in areas with potentials of developing
anaerobic pathogens. Gases utilized in composing the starting atmosphere include
oxygen, CO2, and nitrogen. The commonly used gases for MAP include nitrogen,
oxygen, and CO2. As already established, while oxygen is being consumed during
product storage, the process of respiration generates CO2 [149]. Senescence is delayed
by packaging system through reduction of the rate of respiration, microbial growth, and
metabolic activities [150]. There are two types of MAP based on rate of gaseous
transmission: passive and active. Passive MAP utilizes the natural permeability and
thickness of the packaging film in establishing the necessary atmosphere for the product
due its respiration [151].
MAP has not become popular in the food industry because of the cost of technology
of packaging equipment and materials, the analytical machinery required in ensuring
appropriate gas mixture, and the factor of losing some benefits of MAP on opening the
package or due to leakages. The commonly utilized polymers [152] include polyethylene
terephthalate (PET), polyester, PS, LDPE, ethylene vinyl alcohol, PE, PA, polypropylene
(PP, oriented or not), linear LDPE, and polyvinylchloride [153]. In a bid for the product
to attain the optimum atmosphere, the packaging material must exhibit permeability.
These packaging films may undergo microperforation to enhance interchange of gas
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C. I. IDUMAH ET AL.
between the interior and exterior of the packaging. Xtend® packaging (Johnson
Matthey, Reading, UK) enables packaged product atmosphere equilibration within the
required optimum range of oxygen and CO2 for a specified fruit or vegetable, in
addition to humidity retainment within the package, and weight loss reduction during
storage. Perfo-Tec® laser system conducts appropriate micro-perforations whereby the
film permeability for a specific product is determined (Perfo-Tec BV,
Klompenmakersweg, Woerden, the Netherlands).
MAPs prolong shelf life of fresh food substrates. MAP mode of technology operates
via replacement of the atmospheric air in the interior of a packaging material with a
protective mixture of gas. This gas ensures prolonged product freshness. MAP not only
enables prolonged product freshness but also ensures maintenance of the textural, visual,
and nutritional appeal of packed processed food products. The market segment of MAP
is rapidly growing and forecasted to continue to grow at equal pace over the duration of
this forecast. In accordance with an analysis presented by MRFR, the global MAP market
has predictable growth estimation of CAGR of 5.3% during the duration of this estimation (2017–2023). The global intelligent and AP market share forecast relative to technology including moisture absorbers, temperature indicators, oxygen scavengers, shelf life
sensing, and so on, and by application including food and beverages, personal care, health
care, and so on, have been forecasted to 2023 (MRFR, 2017).
Packaging generally ensures the simplification of the transportation and storage of
goods, which posits a vital role in the functioning of other varying industries including
food and beverage and so on. Some notable factors that have facilitated the growth of
the packaging industry include improvement of the standard of living, consumer’s
health insight, and rapid growth in consumption of packaged foods. Generally, intelligent and APs prolong the food product shelf life, freshness monitoring, degree of
product quality display information, and improvement of safety and convenience.
These are utilized in foods, pharmaceuticals, and numerous other product types.
Fundamentally, smart packaging involves active and intelligent packaging. Here, AP
involves functional packaging over the inert, passively containing and protection of the
product. This also entails intelligent packaging with suitability for interior atmospheric
sphere of the package and also for shipping. This form of packaging ensures adequate
humidity monitoring and control, odors adsorption, and maintenance of the proper
concentration of moisture and gases within the sphere of the packaged products. The
escalating demand for packaged food products, improvement in consumer conveniences, and manufacturers’ aim of attaining prolonged shelf life of the food products
are factors influencing the market share.
However, the high cost of implementation, huge research investment, and growing
demand for the development of superior products are hindering the market growth.
Recently, numerous manufacturers have initiated greater efforts on developing products
at cheaper cost in addition to quality improvement. The active and intelligent packaging
market in 2016 posited an account of $15.11 billion. This market is forecasted to grow
to a value of $23.76 billion by 2023. Technological advancement, provision of alternative innovative packaging, and innovative products availability including the food
industry are the major movers in the global active and intelligent packaging market.
Packaging products that are rapidly emerging include antimicrobial packaging, high-
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25
tech time–temperature monitors, and other packaging products expected to further
grow during the period of forecast.
Recently, emerging market trend reveals that increasing interests of the packaging
companies to focus on prolonging the shelf life of packaged food products are a
determining factor. The conventional packaging systems has failed in meeting up
with the expectations of food products such as meat and frozen foods. These limitations
have resulted in emerging technologies which offer freshness and prolonged preservation to the food products. Progressing government and other agencies interests in
consumers protection on a global spectrum has also ensured longevity inculcation to
food products. This is due to stringent policies of government agencies in setting
standards of food safety, inspections conduction, ensuring compliance to set standards,
and maintenance of strict enforcement. Hence, the active and intelligent packaging
market is globally witnessing a rapid growth. Recent progresses in printed electronics
are encouraging potential growth for the active and intelligent packaging through costs
reduction. However, critical issues such as escalating commodity prices, lack luster
interests of consumers and retailers, and nonchalancy in marketing act as major
limitations for the market growth.
4. Nano-additives/nanoreinforcements in polymeric nanocomposites food
packaging materials
Generally, metals such as silver, copper, gold, platinum, and their alloys and metallic
oxides such as ZnO, Fe2O3, and l2O3 NPs are classified as food safety materials and in
drug administration, hence are utilized as food preservatives [153]. However, the emergence of nanotechnology has resulted in the progress of materials exhibiting novel
physicochemical properties for utilization as effective biocidal agents, nano-biosensors,
and nano-oriented formulations for the detection of food-vital analytes, including gasses,
organic molecules, and food-borne pathogens. The metals and metallic oxide NPs have
exhibited effective biocidal attributes and prospective application in food processing,
packaging, and preservation. Inclusions of polymeric matrices have become imperative
in order to enhance the biocidal and packing properties. Functions of polymeric nanocomposites film for food packaging are schematically elucidated in Figure 7.
Nano-additives or nanoreinforcements utilized in food packaging materials include
nanofibers, nanotubes, NPs, and nanoclay, which synthesis classification is shown in
Figure 8 [5].
Apparently, the most investigated nanofiller is nanoclay or layered silicates and
attributed to their ease of availability, low cost, and superior exhibition. NPs of clay
utilized in fabrication of PNC are typically of several micrometers in length thin (about
1 nm), and two-dimensional sheet (Maisanaba et al. 2018). Montmorillonite (MMT)
having a general chemical formula of (Na,Ca)0.33(Al,Mg)2(Si4O10)(OH)2·nH2O is the
most investigated clay. MMT is soft, 2:1 layered phyllosilicate-clay composed of highly
anisotropic sheets separated by thin layering of water [122].
The nanoplatelets possess an average thickness of about 1 nm and average lateraldimensions ranging between tens of nm to several micrometers (µm). MMT is a 2:1
layered-phyllosilicates, exhibiting platelets with twin-layer sheets of tetrahedral-silica
containing a central octahedral aluminum sheet. Each sheet is composed of a layer of
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C. I. IDUMAH ET AL.
Figure 7. Functions of polymer nanocomposites food packaging films.
Figure 8. Illustration of nanoparticles synthesis.
magnesium or aluminum hydroxide octahedra placed in between twin layering of SiO2
tetrahedra. MMT contains a weak negative charge on the surface which defines the
interlayer spacing. The instability of the surface negative charges is compensated by
cations which are exchangeable including Na+ and Ca2+. A weak electrostatic force
bonds the parallel layers together [154].
The clay is difficult to distribute in organic matrices due to the hydrophilic inclination of the surfaces. Organic nanoclay formed through the interaction of nanoclay and
organic substrates is vital in PNC fabrication. Production of MMTs has been attained
via exchange of its inorganic cations with organic ammonium ions, which enhances its
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27
affinity with organic polymers resulting in better and ordered alignment of the layering
and minimization of the water uptake of the resulting nanocomposite [155].
Through inclusion of less than 5% MMT, improvements in nanocomposite properties such as mechanical properties including modulus of elasticity (MOE), rigidity, and
dimensional stability and thermal properties including thermal stability, barrier properties, and other functional properties such as UV protection, controlled release of
components, and so on are enhanced. NPs decrease clay permeability by about 75%.
PNC fabricated with incorporation of MMT using polymeric matrices such as polyolefins, polyurethanes, PET, PA, PS, and epoxy resins have revealed enhanced barrier
properties [149–156].
Recently, the use of cellulose fillers has proved interesting materials in preparation of
cheap, lightweight, and high-strength nanocomposites [157,158]. In this spectrum,
cellulose chains undergo synthesization in living organisms especially in varieties of
plants as microfiber or nanofibrils coming out as bundles of elongated molecules (with
a 2–20 nm in diameter and micrometers in length) stabilized by hydrogen bonds.
Individual microfiber resulting from the basic fibrils exhibits crystalline and amorphous
phases. The crystalline phases are nanocrystals or nanoplatelets capable of undergoing
isolation via techniques including acid hydrolysis.
Microfibers are revealed as a series of platelets connected by amorphous regions
perceived as structural faults. Also, similarly to nanoclay, the inclusion of cellulosic filler
minimizes the polymer permeability. Various researches have reported improved polymer barrier properties as result of the inclusion of cellulosic filler [116,159,160].
Increased barrier properties were observed on inclusion of less porous cellulosic filler,
uniformly distributed in the polymer with a high filler ratio. As a result of the
hydrophilic surface of cellulose, the interaction occurring between cellulose nanofiller
and hydrophilic matrices is deemed satisfactory [158].
However, the inclusion of cellulosic filler in the hydrophobic polymer causes weak
interactions between the filler and polymer matrix and nanofiller agglomeration due to
hydrogen bonding. The high water absorption affinity due to the hydrophilic nature of
cellulosic nanofiller is a significant undesirable factor in most applications. These
challenges can potentially be reduced by various modifications such as hydrophobization on the cellulose surface via numerous hydroxyl groups’ reactions such as esterification and fatty-acid acylation [161].
Trademarked polymer composites utilized in packaging include Imperm® (Color
Matrix Europe) – utilized in multilayer PET sheets and bottles for beverage and food
packaging to reduce permeation of O2 and loss of CO2 from beverages. Another is
Duretham® KU 2-2601 (LANXESS Deutschland GmbH) – nanocomposite films fabricated from PAs with enhanced properties when superior barrier properties in
packaging juices are imperative. Another is Aegis® OX (Honeywell Polymers), a
PNC film composed of a blend of active and passive nylon incorporating active O2
scavengers and passive nanocomposite clay particles to improve barrier properties.
4.1. Cellulosic NP reinforcements
Cellulose is the major building block of lengthy fibrous cells and a highly strong
naturally occurring polymer. Cellulose nano-fibers are not expensive and are
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C. I. IDUMAH ET AL.
commonly assessable material. Additionally, they are eco-benign and easily recycled
via combustion, and consume less energy during production. The application of
nanotechnology is rapidly expanding the concept of antimicrobial packaging [162].
A very recent work investigated influence of nanocellulose (NC) and Ag NPs on the
mechanical, physical, and thermal properties of PVA nanocomposite films. Results
revealed that material tensile strength improved from 5.52 ± 0.27 to 12.32 ± 0.61 MPa
when reinforced with 8 wt% of NC. The films revealed strong antibacterial activity
against both Staphylococcus aureus (MRSA) and E. coli (DH5-alpha). Also, rate of
water vapor transmission was minimized with the inclusion of NC and Ag NPs [163].
Hence, subsequent properties present cellulose nano-fibers as attractive set of nanomaterials relative to their high strength, lightweight, and low cost [164].
Fundamentally, two major forms of nano-reinforcements are derivable from cellulose.
These include microfibrils and whiskers [165]. Naturally, cellulosic chains undergo
synthesis resulting in the formation of microfibrils or nanofibers, which constitute a
set of molecules that are elongated and stabilized through hydrogen bonding [166].
Studies reveal that microfibrils exhibit nano-sized diameters of about 2–20 nm,
depending on the orientation, and micrometer ranged lengths [167,168]. A single
microfibril is created through agglomeration of primary fibrils, which are composed
of both crystalline and amorphous components. Whiskers, nanocrystals, nano-rods,
or rod-like cellulose microcrystals are the crystalline components of the matrix and
can undergo isolation via various routes [159–168], exhibiting lengths within range
of 500 nm, and about 8–20 nm or smaller in diameter, which inculcate high aspect
ratios. A single unit of microfibril is composed of aligned stretches of whiskers,
connected by amorphous sections containing some structural deficiencies, and
exhibiting modulus near to that of the original crystal cellulose of about 150 GPa
and a strength of about 10 GPa [168]. The major route of deriving cellulose whiskers
is acidolysis, composed mainly of eliminating the amorphous zones within the fibrils
while maintaining the crystalline zones [169]. Microcrystalline cellulose (MCC) is
fabricated through elimination of the amorphous zones via acid degeneration which
maintains the poorly accessible crystalline zones of length 200–400 nm and aspect
ratio within range of 10.
4.2. Carbon nanotubes (CNTs)
CNTs are made up of single atoms thick single-walled nanotubes, or composed of
circular tubes referred as multiwalled nanotubes, exhibiting extremely high elastic
modulus and aspect ratios [91]. Research has revealed CNTs possess theoretical
elastic modulus and high tensile strength values of about 1 TPa and 200 GPa,
respectively [170]. Also, CNTs have undergone modification via introduction of
carboxylic acid groups so as to improve their interactions intermolecularly with
the polymer matrix [171]. Results revealed that inclusion of small amounts of
CNTs greatly enhanced thermal stability, tensile strength, and modulus of the
matrix. Another study revealed enhanced tensile strength and modulus of PVA
through inclusion of CNTs [172].
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In a recent research, a comparative study of pectin composites in conjunction with
CNTs was prepared by chemical interaction or physical mixing [173]. Results revealed
films with appropriate properties for packaging applications.
Another research revealed a PLA-CNT nanocomposite showed a 200% superior
water vapor transmission rate (WVTR), toughness, and modulus in comparison with
pristine PLA [34,173]. It is already established that polymer-oriented packaging films
are versatilely utilized in packaging to preserve various types of foods and confectionaries. A polymer commonly utilized in the production of packaging films is isotactic
polypropylene (iPP) and its copolymers with PE, due to its cheapness, good mechanical
properties, and superior optical properties [65].
However, these polyolefins are apolar and exhibit hydrophobic attributes.
However, it is established that polymers exhibiting hydrophobic attributes release
static electricity during processing which causes dangerous explosions and emit dust,
giving an expired appearance to the food package [174]. Currently, the static
electricity challenge in iPP films is eliminated through inclusion of antistatic additives in the formulation. Thus in a recent research, CNT was used in the fabrication
of iPP-transparent low electrostatic charge film. Results revealed effective packaging
film for food and confectionaries.
In a recent investigation, MWCNTs was utilized in exterior layers (A-layers) of
ABA-trilayer PP films, with the objective of finding the intrinsic and extrinsic factors
causing the antistatic attributes of transparent films. The inclusion of 0.01, 0.1, and 1 wt
% of MWCTNs in the A-layers was conducted using the masterbatch technique. It was
revealed that films composed of MWCNTs exhibited surface electrical resistivity of 1012
and 1016 Ω/sq, despite the iPP melt flow index (MFI) and type of masterbatch fabrication technique [175]. This is elucidated in Figure 9.
4.3. Silica (SiO2)
nSiO2 have reportedly enhanced the mechanical and barrier attributes of various
matrices of polymers [176–178]. In a recent study, bitter-vetch protein films underwent
structuring using mesoporous nSiO2. Results showed improved tensile strength and
elongation at break. Moreover, material gas and water vapor permeabilities reduced as a
result of the NPs inclusion. Results revealed that crosslinking of protein using transglutaminase improved the barrier properties of the film. Moreover, all films offered
antimicrobial and antifungal efficiency [176].
In general, polymer composites fabricated using silicate NPs as nanofillers at low
level of inclusion revealed improvement in mechanical and physicochemical properties
when compared with pristine polymers. Inclusion of NPs as reinforcement for pristine
polymers has proved to be a highly prospective option at improving the mechanical and
barrier properties of materials in fabricating nanocomposites [179].
Researches have revealed that inclusion of SiO2 into a PP matrix enhanced the
material mechanical properties (tensile strength, modulus, and elongation) [180,181].
Emerging trends in SiO2/polymer hybrid composite materials have combined the
special properties of inorganic fillers and organic polymers in fabricating organic/
inorganic nanocomposites. In order to enhance recognition of interfacial interaction
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C. I. IDUMAH ET AL.
Figure 9. Optical micrographs of ABA films fabricated via masterbatch with MFI = 34 g/10 min. The
masterbatches were fabricated via ultrasound-assist technique V-U. (a) 0.1 wt% MWCNT and (b)
1.0 wt% MWCNT in the A-layers. Photograph of ABA films: (c) reference film, 0 wt% MWCNT, (d) film
with 1 wt% MWCNT (fabricated with masterbatch: iPP MFI = 2.5, F-U), and (e) film with 0.01 wt%
MWCNT (fabricated with masterbatch: iPP MFI = 2.5, V-U). TEM micrographs for ABA film containing
1.0 wt% MWCNT in the A-layers fabricated using masterbatch with MFI = 34 g/10 min with
ultrasound-assist method V-U. (f) MWCNTs near to each other, (g) MWCNTs touching to each
other, and (h) SEM micrographs for ABA film containing 1.0 wt% MWCNT in the A-layers fabricated
using masterbatch with MFI = 34 g/10 min with ultrasound-assist method V-U. The optical attributes
of films composed of MWCNTs did not exhibit significant variations in comparison to the reference
film at MWCNT concentrations below 0.1 wt%. However, improved brightness was observed, and
ascribed to well-arranged iPP molecules engulfing the MWCNTs [175].
and nanoscale hybridization of organic polymers and silica fillers, a new route has been
introduced to synthesize hybrid nanotechnological materials [182].
In a study, biodegradable starch/copolyesters/silica nanocomposite films underwent
preparation via melt-extrusion, utilizing twin-screw extruder and blown-extrusion
machinery. The effect of nSiO2 inclusion on mechanical and thermal properties of
nanocomposite films revealed that inclusion of 2 wt% SiO2 in PBAT/Starch matrix,
improved material mechanical properties [183].
In a recent study, silica gel was derived from rice husk as lightweight and cheap
biomaterial and subsequently incorporated into a cross-linked alginate utilized in
preparation of a nontoxic and functional nanocomposite material. Alginate/silica
hybrid was studied as a template for the formation of ZnO. NPs of ZnO having
diameters of ca. 20 nm were uniformly positioned into alginate/silica hybrid. The
antibacterial properties of the material were assessed against Gram positive (S. aureus)
and Gram negative (E. coli) bacteria. Results revealed that the alginate/silica/ZnO
nanocomposite is a potentially sustainable and disinfectant material suitable for efficient
bacteria inhibition [184].
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31
In another study, Starch/PVA/CaCO3 nano-biocomposite films were fabricated via
solution casting technique. Results revealed that the fire retarding, tensile strength and
thermal attributes of the materials were improved with increasing CaCO3 percentage.
With increasing inclusion of nano-CaCO3 in starch/PVA/CaCO3, the oxygen permeability (OP) of the film was decreased. Overall, the improved fire retardancy, thermal
stability, tensile and oxygen barrier properties of the nanobiocomposite demonstrate a
potentially useful material for packaging application [156,185].
Different ternary films were fabricated using varying ratios of starch/PVA/citric acid.
Overall, results revealed strong antimicrobial efficiency against Listeria monocytogenes
and E. coli, the food-borne pathogenic bacteria utilized in testing antimicrobial efficiency. Freshness analysis results of fresh figs revealed that all of materials inhibited
condensed water formation on the film surface, while the S/P/C 3:1:0.08 and S/P/C
3:3:0.08 hindered the figs deterioration during storage. The results demonstrated
potential use of the films as active food packaging as a result of their strong antimicrobial efficiency [186].
Generally, mechanical strength is needed in the maintenance of structural integrity
and barrier attributes of thin films. Results from researches have shown that NPs improve
longitudinal strength, water vapor permeability (WVP), and OP of polymeric films with
potentials of improving the barrier and mechanical properties of the films [187].
These enhancements in properties result in protection of food products against
degradation, prolonging of the shelf life of foods and maintenance of food quality.
Mass transport is the mechanism of gas permeation through PNC and is similar to that
obtainable in a semicrystalline polymer matrix. Ab initio, gas molecules are usually
adsorbed on the polymer surface during gas permeation, and this diffuses through the
polymer. The polymer region is thought to be permeable in a nanocomposite, while
silicate sheets are thought to be non-permeable to gases [188].
In a research, inorganic nano-silica was incorporated into PLA as an organic
reinforcement with a biodegrading attributes in the preparation of biodegradable
organic/inorganic hybrid coating material via the sol-gel process. Results revealed
enhancement of the water vapor and gas barrier properties of PLA/SiO2 nanocomposites films with the capability of being utilized as coating films in food packaging [189].
Hence, the barrier disposition of a polymer film can be elucidated relative to
permeability depending on the coefficient of gas diffusion and the solubility coefficient
expression of the gas in the polymer matrix. Research has revealed that polycaprolactone-reinforced SiO2 NPs have prospects of being utilized as a polymer-oriented
nanocomposite system [190]. Thus, recent researches have revealed the efficacy of
inorganic and metal NPs as antimicrobial barrier in food packaging functionalization
[191–193]. Recent studies involving biosynthesis of AgNPs and polyhydroxybutyrate
nanocomposites have revealed efficacy in use as antimicrobial material [83]. Recent
studies of the effect of SiO2, PVA, and glycerol concentrations on chemical and
mechanical properties of alginate-based films have revealed improved materials suitable
for antimicrobial activities hindering packaging films [97].
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4.4. Nanocrystals of starch
The local starch flour undergoes prolonged hydrolysis at lower temperatures compared
with the gelatinization temperature, on hydrolysis of the amorphous zones which
encourages hydrolysis-resistant lamellae crystals to separate [194]. The NPs of crystalline starch with 6–8 nm exhibit platelet morphology [195].
In a recent study, a glucoamylase pretreatment was utilized in the fabrication of
starch nanocrystals. The results revealed minimized preparation duration with very
small nanocrystals. The nanocrystals exhibited high stability, crystallinity, and dispersibility [196]. The ultrasound enabled preparation of starch nano-sized particles (SNP)
has been reported. Dynamic light scattering (DLS) and Field Emission Scanning
Electron Microscopy (FE-SEM) observation were used in confirming the nanosize
attribute. The sheet type morphology was confirmed via small angle x ray
scattering (SAXS). Results demonstrated a potentially feasible packaging film. In
another investigation, irradiated-corn-starch films were developed and characterized.
Here, gamma ray irradiation was used at reducing starch crystallinity. Gamma ray
irradiation was revealed to cause reduction in the dispersion of larger particles of starch.
Elevated irradiation improved the starch films tensile strength. A higher degree of
irradiation was found to reduce the WVP of starch films. The irradiated-corn-starch
films exhibited prospects as a biodegradable starch film with enhanced properties [197].
The fabrication and subsequent characterization of nanocrystals of starch via ball
milling in conjunction with acid hydrolysis has been conducted. The best ball milling
duration for the fabrication of SNCs was ascertained. An authentic technique for the
preparation of SNCs in short duration of time and with increased yield was proposed.
Feasibility of material utilization in packaging was ascertained high [198].
In another recent research, tunable D-limonene permeability in starch-oriented nanocomposites films filled by CNC was conducted. This investigation offered interesting
elucidation for control of the flavor emitted from starch-oriented films, which promoted
its utilization as a biodegradable food packaging material and flavor encapsuler [199].
A recent research elucidated the efficiency of derived CNC and SNP and the technofunctional properties of films produced. Results revealed that CNC and SNP exhibited
significant physical and mechanical characteristics. The derived attributes significantly
facilitated their utilization as superior performing constituents of bio-oriented packaging films and available alternatives of their petroleum-oriented contemporaries. The
present research elucidated a time-effective and cost-effective derivation technique of
CNC and SNP via sulfuric acid hydrolysis and neutralizing mechanism. The potentials
of utilization as antimicrobial films were highly elucidated in this studies [200].
The effect of CNC on mechanical, moisture absorption, barrier, glass transition
temperature (Tg) and melting point temperature (Tm) behaviors of LDPE and thermoplastic starch composites have been studied [201]. Results revealed that mechanical
properties (tensile strength, MOE, and hardness) were significantly enhanced by CNC.
Higher Tg and Tm of CNC nanocomposites were higher in comparison to nanocomposites devoid of CNC. Moreover, water absorption was remarkably reduced as a result
of the inclusion of CNC to LDPE/TPS composition. In addition, the coefficient of WVP
and WVTR were significantly reduced as a result of the inclusion of CNC. Thus, this
implies that CNC significantly enhanced the barrier properties of LDPE/TPS
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33
composites. Inclusion of 1% CNC to LDPE/TPS combination revealed the optimum
degree of incorporation of CNC resulting to most superior level of strength enhancement and optimum barrier performance of LDPE/TPS which is satisfactory and appropriate as acceptable tensile strength for extruded and molded LDPE [201].
In a recent study, the influence of poly (3-hydroxybutyrate-co-3-hydroxyvalerate)
microparticles on thermal, morphological, barrier, and mechanical properties of thermoplastic potato starch films has been conducted. Results of humidity absorption
analysis exposed that the high degree of starch hydrophilicity was minimized on
inclusion of PHBV microparticles. Additionally, increasing inclusion of PHBV microparticles minimized the rate of water vapor transmission. However, specimens with
lower content of glycerol exhibited decreased levels of humidity absorption and lower
rate of water vapor transmission. SEM micrographs revealed homogeneous surfaces for
biocomposites with decreasing inclusion of glycerol. Dynamic mechanical analysis
elucidated poly (3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) reinforcement influence on the microparticles within the matrix. Thermogravimetric analysis (TGA)
demonstrated that presence of PHBV microparticles improved starch thermal stability [202].
Starch can be used in formation of biodegradable containers and films because of its
ease of processability, low cost, filmogenic, and wide availability [203]. It can also be
utilized as a viable alternative to polymers extracted from petroleum. In addition, starch
could also be utilized in the creation of edible coatings for fresh foods so as to prolong
material shelf life. Hence, wheat starch films composed of two glycerols have been
formulated to imitate the effects of substances presently utilized in fruit coating. Results
revealed a material potentially suitable as a packaging film [204].
The strength of HPMC-starch films has been enhanced through inclusion of nanocrystals of cellulose. This is as result of the increasing interest CNC derived from
natural resources has garnered due to the unique properties achieved in their composite
materials. Thus, a recent study evaluated the influence of CNC inclusion on mechanical
properties of bio-films obtained from hypromellose or HPMC and blends of cassava
starch. Results demonstrated that nanocrystals reinforcement resulted in improvement
in the film’s mechanical properties, and their fractured surface revealed that CNC
enhanced the hypromellose and starch molecules cohesion in the blend, while enabling
greater surface homogeneity [78].
In another study, transparent, UV-resisting bio-nanocomposite films based on
potato-starch-cellulose for sustainable and improved packaging experience have been
produced. Bio-originated polymers have been considered as potential alternatives for
traditional synthetic plastics from fossil fuels to compensate for the depleting petroleum-based by-products, in addition to environmental compliancy. Hence, in present
study, cellulose nanofibers underwent isolation from pineapple leaves while the quality
of the prepared nanofibers was ascertained via advanced techniques. It has been
established that the poor mechanical, barrier, and hygroscopic nature are notable issues
that minimize the shelf life of starch-originating films, which can be recompassed
through the inclusion of nanofillers. Relative to the reference specimen, enhanced
packaging properties were observed.
In a recent study, AP film was developed through incorporation of β-carotene starch
nanocrystals [205]. Results revealed effective packaging material. A recent study
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C. I. IDUMAH ET AL.
attained ternary films through utilization of PVA as matrix and nanostructured starch
(starch nanocrystals) as reinforcing phase with hydroxytyrosol (HTyr), a phenolic
compound found in olive oil, as antioxidizing agent [206]. The fabricated multifunctional films were characterized relative to optical, morphology, and thermal properties;
water absorption propensity; specific mobility as food stimulant and antioxidant attributes. Results revealed a strong antioxidation activity. Overall, PVA reinforced with low
amylose starch and HTyr NPs developed a potential ternary material for food packaging
applications. Another study prepared and characterized starch-based composite films
reinforced using polysaccharide crystals. Results revealed transparent and smooth surface appearance. The inclusion of crystals improved Young’s modulus and tensile
strength of starch-based materials while reducing elongation at break. SEM analysis
revealed good compatibility between starch matrix and the reinforcement fillers as a
result of glucose unit. Overall, the developed films proved to be biodegradable and safe
for food packaging with potential application as edible films for wrapping for candies
and medicinal soft and hard capsules.
Ternary nanocomposite films possessing good properties were prepared through
inclusion of two varying types of NPs namely rice starch nanocrystals and AgNPs in
conjunction with PVA matrix at varying concentrations. Results revealed that enhanced
chemical, mechanical, and thermal properties are good for packaging applications [207].
Starch-based materials are attractive materials as a result of their eco-friendly disposition.
Moreover, these biopolymers in addition to partly replacing existing plastics in
multiple applications also offer new materials with functional properties. Though
non-biodegradable petroleum-oriented plastics still remain most domineering materials
utilized for packaging in the food industry for packaging, widespread utilization of
these conventional materials has resulted in serious negative environmental challenges.
Various studies have been conducted in previous years to replace these packaging
plastics with eco-benign materials in a bid to alleviate the present plastic waste disposal
issues [208,209].
In a recent study, Tapioca starch active nanocomposite films and their antimicrobial
efficiency on ready-to-eat chicken meat were investigated. Tapioca starch active nanocomposite films were fabricated through inclusion of CNC and two grape pomace extracts
(Cabernet Franc (red variety) and Viognier (white variety) utilizing a solvent casting route
[210]. Results revealed that the films incorporating grape pomace extracts showed a
superior limiting effect on S. aureus ATCC-29213 in comparison with L. monocytogenes
ATCC-7644. Further use of the films on ready-to-eat chicken meats indicated that starch/
CNC/Viognier films exhibited superior efficiency against L. monocytogenes inoculated on
the meat specimens during the 1 week and 3 days storage period at 4°C [210].
A two-step surface modification method can be used to modify the surface hydrophobicity of starch-oriented film by grafting with alkanols of varying chain lengths such
as hexanol, dodecanol, and octadecanol on the surface of starch-oriented films.
Improved film packaging properties were observed [211].
A recent investigation studied the structural and physicochemical analysis of microalgae thermoplastic corn starch films [212]. This research provided deep studies on how
inclusion of various microalgae species (Nannochloropsis, Spirulina, and Scenedesmus)
influenced the structural and physicochemical attributes of thermoplastic corn starch
biocomposites. Results revealed decreased WVP by ca. 54% on inclusion of varying
COMPOSITE INTERFACES
35
species of microalgae. The OP and mechanical attributes of biocomposites containing
Spirulina or Scenedesmus were not enhanced because the presence of microalgae
restricted proper arrangement and packing of starch lamellar structure of polymeric
chains relative to the SAXS results. Nannochloropsis induced large decrease of the
matrix rigidity while OP was also enhanced. A recent study investigated and characterized bio-nanocomposite films based on CS or chitosan, filled with MMT or bamboo
nanofibers [213]. Results revealed improved barrier properties of the film for enhanced
packaging activities.
A recent investigation studied the preparation and characterization of nanocrystalline cellulose/Eucommia ulmoides gum nanocomposite films [166]. Results revealed
enhanced barrier properties for effective packaging.
In a recent investigation, recycled gelatin-starch composite films were fabricated via
extrusion: physical and mechanical properties [214]. Morphological results revealed
that the films exhibited a cohered matrix with no phase separation. The crystallinity
analysis revealed that the extrusion process was devoid of granular crystalline zones
resulting in the production of low-crystalline films. The inclusion of recycled gelatin
resulted in improved thermal stability while remarkably improved the mechanical
strength and water solubility of the films. Acceleration of the biodegradation process
was observed. Thus, it was concluded that the recycling and reprocessing effect did not
influence gelatin properties, though it significantly affected the films properties.
4.5. Silver NPs
As a result of strict environmental policies, the packaging industry has been investigating economically viable biodegradable food packaging materials with appropriate properties and eco-benign. Biopolymeric materials including chitosan and gelatin have
positioned as potential alternative materials to plastic packaging materials, with appropriate packaging functions and biodegradable attributes.
Thus, in a recent work, a hybrid nanocomposite film composed of chitosan, gelatin,
PE glycol, and AgNPs was fabricated via solution casting technique. Different films
were prepared with varying composition of AgNPs and chitosan. Nano-Ag inclusion
resulted in enhanced mechanical attributes and reduced light transmittance in visible
light region. Nevertheless, transparency studies, XRD, SEM, and optical microscopy
revealed transparent and homogenous tendencies for all prepared films demonstrating
the even dispersion of the components in the films. However, on use of this film in
packaging red grapes, results revealed prolonged shelf life of the fruit for extra 2 weeks
for the hybrid film portending potentials of this film as candidate film for fruit
preservation [207].
An established disadvantage of polymers when utilized in direct food-contact applications is their affinity for microbial degradation. Nevertheless, AgNPs have attracted
increasing interests as effective antimicrobial agents. Hence, the inclusion of AgNPs
into traditional polymers has resulted in new materials exhibiting enhanced properties.
In the present study, colloidal AgNPs exhibiting an eco-benign affinity were synthesized. Results revealed antimicrobial efficiency against both Gram positive and negative
bacteria, such as Bacillus cereus, Bacillus subtilis, E. coli, and S. aureus [215].
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C. I. IDUMAH ET AL.
Masterbatches of twin polymers were utilized in developing nanocomposite films.
These polymers include LDPE and PP with inclusion of AgNPs, attained via melt
compounding and melt extrusion. During the procedure, it was observed that the
yellowing of the films increased with increasing inclusion of Ag. Morphological
analysis demonstrated efficiency of Ag inclusion in the polymers. The LDPE-Ag
nanocomposite film demonstrated a similar strength comparable with commercial
LDPE, with increasing stiffness at high Ag (240 mg/kg) concentration. On the other
hand, the Ag/PP nanocomposite film demonstrated improved mechanical properties
in comparison with commercial PP. Nevertheless, high Ag inclusion of about
290 mg/kg also caused films weakening. Overall, the nanocomposite films demonstrated efficiency against E. coli and S. aureus at 36 and 30 mg/kg concentration of
Ag NPs for Ag/LDPE and Ag/PP films, respectively, which lead to >99.9% reduction
in the volume of bacteria. The influence of antibacterial was more visible on S.
aureus indicating that the produced nanocomposite films exhibited high prospects
for antimicrobial food packaging film development [216].
A recent investigation revealed a low-cost and eco-benign technique for AgNPs
synthesis utilizing the wild mushroom Ganoderma sessile. Test results revealed the
controlling effect of synthesized AgNPs against the development of food-borne pathogens with potential utilization in the food packaging sector. Results demonstrate
potential suitability as antimicrobial packaging film [217].
In a recent investigation, TiO2-Ag NPs (3% and 5%) were distributed in LDPE via
melt extrusion, and nanocomposite films prepared via hot pressing. Results revealed
enhanced mechanical properties of the nanocomposite films on utilizing paraffin as
compatibilizing agent when compared with pristine LDPE films. Optical investigation
revealed that inclusion of TiO2-Ag to LDPE films hardly affects the appearance of the
film but influences them to be more reddish in color. Thus, this study fabricated a
material suitable for food packaging though further study is required to confirm this
attribute. Hence, results revealed that both TiO2-Ag NP and compatibilizing agent are
required to hinder the growth of bacteria in the film. Superior result was derived by
utilizing 5% NP and 4% paraffin compatibilizing agent respectively which remarkably
minimized the rate of bacteria development by 95% [218].
In a recent investigation, mucus and microbiota as new players in gut nano-toxicology have been undertaken [219]. Instances of dietary silver and TiO2 NPs have been
used. Due to escalating interest in nanotechnology in several available consumer goods,
including foods, analysis of the implication of extreme exposure of humans to NPs has
become a critical public health challenge. Nevertheless, the oral mode of exposure has
not being fully explored, despite the availability of a certain level of NPs in some food
supplements, additives, and the inclusion of such particles in packages in contact with
foods. Post ingestion, these NPs move through the digestive tract, and potentially go
through physicochemical transformations, with implications for the luminal environment, prior to moving across the epithelial cover to attain the systemic region [219].
In another recent investigation, Ag NPs that were uniformly distributed in HDPE
matrix underwent UV exposure with rapid degradation of HDPE. As a result of
chemical scission, new bonds (hydroxyl, vinyl, and carbonyl) were created. Results
confirmed substantial stabilization of HDPE against UV irradiation by Ag NPs.
Moreover, HDPE thermal decomposition was notably not affected by Ag [220].
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37
The most popular route of preparing Ag-NPs into colloidal, stable dispersion is via
chemical reduction [221]. The reducing activity of Ag+ in aqueous solution results in
colloidal-silver exhibiting particle diameters in nanometers. Ab initio, this reducing
activity results in Ag atoms formation (AgO) and their agglomeration into oligomeric
clustering resulting in formation of Ag-particles [222]. Systematic mechanisms have
been proposed for the antimicrobial affinities of AgNPs [81]. These mechanisms
include cell surface adhesion, membranous ‘crevices’ formation, lipo-polysaccharides
degradation, and improved permeability penetration of bacteria cell, DNA degradation
[223], and antimicrobial Ag+ ions release through dissolution of Ag-NPs [224].
The effect of polymers and surfactants on agglomeration stabilization and antimicrobial activities of Ag-NPs has been conducted. Results revealed that the bacteria effect
of modified AgNPs had improved bactericidal effect [225]. A connection reportedly
existed between agglomeration stability and antibacterial interactions. AgNPs have
undergone successful testing as antimicrobial material [3,226]. Trace quantities of
AgNPs exhibiting broad surface area ready for interacting with the cells of microbes
result in efficient bactericidal influence than large particles of Ag [227,228].
Numerous researchers have fabricated and investigated the antimicrobial effect of silver
nanocomposites. A comparative analysis of the effectiveness of PA 6-silver-nano- and
micro-composites revealed that nanocomposites possessing low inclusion of silver exhibited superior efficiency toward E. coli in comparison with micro-composites exhibiting
higher concentration of silver [229]. Also another similar comparative investigation
reported that PA 6 reinforced with 2 wt% AgNPs was efficate against E. coli, despite
water immersion for 100 days. Nevertheless, ethylene is absorbed and decomposed by
AgNPs which contribute to its influence on prolonging the shelf life of vegetables and fruits.
Also, another investigation revealed that PE/Ag-NPs nanocomposite hindered the
jujube fruit senescence [82]. In a study, a coating composed of AgNPs was efficient in
reducing the development of microbes while improving asparagus shelf life [230]. Also,
Ag-NPs reportedly enhanced strength, modulus, thermal and stability properties while
improving its transition temperature [191]. On the other hand, nanostructured calcium
silicate (NCS) was utilized in adsorbing silver from solution down to the 1 mg kg−1
level. The fabricated NCS–Ag composite revealed efficient antimicrobial activity at
desirably low levels of silver down to 10 mg kg.
TiO2 is broadly utilized as a photocatalytic disinfectant for surface coatings [231]. A
research has produced TiO2 flour-coated packaging film capable of reducing E. coli-conon
contamination on food surfaces, inferring that the film could be utilized for freshcut
products [231]. Another research revealed efficiency at inactivating fecal coliforms in
water by TiO2-coated films exposed to sunlight [232]. The doping of metals enhances
absorption of visible light by TiO2 while also increasing the photocatalytic effect of UV
irradiation [233]. Research has also revealed that TiO2 doping with silver also enhanced
weakening of photocatalytic bacterial [234]. The inclusion of TiO2 with silver has been
utilized in obtaining efficient antimicrobial attributes from NPs of TiO2-Ag+ in PNC [118].
While the fabrication and functional evaluation of thin film zein with inclusion of spindlelike ZnO crystals demonstrated efficiency at antimicrobial activities [235].
The antibacterial attributes of chitosan have been revealed in a recent research [39].
A potential antibacterial mechanism has been hypothesized relating to the interactions
between positive charges of chitosan and negative charges of the cell membranes which
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increased the permeability of the membrane while finally rupturing and leaking the
intracellular material. This aligns with the revelation that both pristine chitosan and
engineering NPs are not effective above pH values of 6, as a result of the lack of amino
groups of protonation [236]. A twin antimicrobial mechanism has been put forward in
a research. These include chitosan chelation by trace metals which retards enzyme
activities and, in cells of fungus, penetration via the membranes and cell wall so as to
facilitate DNA binding and retardation of the synthesis of RNA [237].
Investigation into the influence of AgNPs inclusion on bisphenol A migration from
polycarbonate glasses into food stimulants has been conducted. Insight into antioxidant
and antimicrobial methylcellulose films containing Lippia alba extract and AgNPs has
also being conducted revealing positive effects of AgNPs inclusion for effective antimicrobial packaging [238].
The advent of nanotechnology has introduced drastic changes to almost all the fields
of science and technology, especially the food packaging industry. Thus, varieties of
NPs can be utilized in food contact materials to prolong the food shelf life [191].
Nowadays, varieties of inorganic and metallic NPs have been utilized in synthesizing
active food packaging materials and to prolong the shelf life of foods. Nanocomposites
packaging materials composed of these NPs provide benefits, such as reduction in the
utilization of preservatives and elevated reaction rate to hinder the growth of microbes.
However, the safety challenges of using metallic and inorganic NPs in food packaging
materials pose critical issues and thus require more studies [191].
In a recent research, poly (lactide)/lignin/AgNPs composite films containing UV
light barrier and antibacterial properties were prepared [239]. Results revealed that the
mechanical and water vapor barrier properties of the composite films were improved
post inclusion of lignin and AgNPs. The films composed of AgNPs revealed high
potency for antibacterial activity against E. coli and L. monocytogenes.
In a study, an active film has been fabricated through inclusion of cortex
Phellodendron extract (CPE, an active agent) into a soy-bean protein isolate (SPI).
The influence of CPE content on antibacterial and antioxidant activities of the films was
studied. The results revealed that novel hydrogen bonds were formed between molecules in the films, and the crystallinity of the films was reduced. CPE inclusion revealed
zero effect on the thermal stability of the films. The barrier properties against water
vapor, oxygen, and light were improved with the inclusion of CPE. The antioxidant
effect of SPI film was also improved. The films exhibited efficiency against S. aureus
(Gram-positive bacteria). These results imply that the SPI/CPE film can prospectively
enhance the shelf lives of foods [240]. This is elucidated in Figures 10 and 11
respectively.
5. Nanosensing and biosensing in food packaging
5.1. Nano-based sensors
NPs exhibit potentials of application as reactive particles in packaging materials. Nanosensors have the capability of responding to environmental variations such as temperature, pressure or humidity in storage rooms, degrees of exposure of O2, and products of
degradation or microbes’ contamination [241].
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Figure 10. (A) Scanning electron microscopy (SEM) micrographs of the surface (s, left) and cross
section (cr, right) of the (a) SPI and (b) SPI/CPE films. (B) (a) thermogravimetric analysis (TGA) and (b)
differential thermogravimetric analysis (DTG) curves of the SPI-based films [240].
Figure 11. (a) The antibacterial activity of the CPE and films and (b) antioxidant activity including total
phenol content (TPC) and 2,2-diphenylpicrylhydrazyl (DPPH) scavenging activity of the films [240].
The conditions which food materials are exposed to relative distribution and storage
especially temperature to which the food product is exposed are used by industries in
estimating the food expiration date. On integrating nano-sensors into food packaging,
the capability to detect toxins, pathogens, and certain chemical compounds in food, in
addition to eliminating the need for inaccurate expiration dates, and provision of the
actual status of food freshness is inculcated into them [242].
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C. I. IDUMAH ET AL.
The potential of nano-based sensors in detection of pathogens, deterioration, chemical contaminating agents, or product tampering, or to the tracking of ingredients or
products via chain of processing has globally being acknowledged [13]. The deterioration of food is induced by microbes, whose metabolic activities generate gases capable
of detecting conductive polymer nanocomposites (CPC) or metallic oxides, capable of
being utilized for quantification and/or identification of microbes depending on their
gaseous emissions. CPC sensors consist of conducting particles inculcated in an insulating polymer matrix. Flexy glucose sensor has capability of giving insight into
biomedical devices. Thus, recently a new scaffold oriented on vertically arranged
CNTs and a conjugated polymer has been fabricated [243]. This elucidated beneficial
enzyme immobilization as a result of conductive polymer and vertically arranged CNTs
resulting in a sensitive and prolonged life glucose biosensor.
The variations in resistance of the sensors generate a pattern corresponding to the
studied gas [2]. In a study, CPC sensors composed of carbon black and polyaniline was
developed to enable the detection and identification of food-borne pathogens via the
generation of a unique pattern of response for individual microorganism [244]. Three
types of bacteria namely B. cereus, Vibrio parahemolyticus, and Salmmonella spp were
identified from the style of response patterning generated by the sensors.
An electronic tongue capable of inclusion in food packages which function of
sensing food degenerative gases released by food spoilage microbes has been developed.
This device is made up of a group of gas-sensitive nano-sensors capable of inducing a
color variation indicating deteriorated food. Oxygen indicating devices hinder the
growth of aerobic microorganism on food during storage. Recently, interests in development of irreversible and nontoxic oxygen-sensing devices have escalated in order to
ensure absence of oxygen in oxygen-free food packaging systems, existing in vacuum or
nitrogen packaging systems.
In a research, an ultra violet inducing oxygen colorimeter, utilizing titania nanoparticles (TiO2) in photosensitizing the minimization of MB by tri-ethanolamine in an
encapsulating polymer medium, via UVA lighting was developed. Here, on UV irradiation, the sensor undergoes bleaching while remaining colorless, until it undergoes
oxygen exposure, on restoration of its original color of blue. The degree of recovering
color is proportional to the magnitude of exposure to oxygen.
In another study, MB-TiO2 nanocomposite thin films were deposited on a glass via
liquid-phase deposition. This is a subtle chemical method utilized in depositing oxides
to numerous materials. This method could be utilized in developing oxygen indicating
packaging systems for a wide range of oxygen-sensitive foods [245].
In another study, nanocrystalline SnO2 was utilized as a photosensitizer in an
oxygen-colorimetric indicating device composed of a free electron donating glycerol,
a redox-dye MB, and polymer encapsulation hydroxyethyl cellulose. Also, SnO2 inverse
opal composite film with low-angle-dependent structural color and enhanced mechanical strength has been investigated. UVB light exposure resulted in activation and
photobleaching by the indicating device revealing photoreduction of MB by the SnO2
NPs. The films color changed as function of exposure to O2 such that it indicates
bleaching when unexposed, and blue color when exposed [242].
Embedded nano-sensors in the packaging will alert the consumer if a food has gone
bad. The use of protective coatings and suitable packaging by the food industry has
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41
become a topic of great interest because of their potentiality for increasing the shelf life
of many food products [246]. By means of the correct selection of materials and
packaging technologies, it is possible to keep the product quality and freshness during
the time required for its commercialization and consumption [247].
5.2. Biosensing in food packaging
Nowadays, intelligent and active food packaging systems enhance sustainable quality
and safety of foods, effective controlling of the packaging process, and enhanced shelf
life to meet the high requirements from manufactures and consumers. Nanomaterials
are included in food packaging for biosensing, prolonged shelf life, intelligent and
robotic technologies in order to enhance education and awareness of the consumer
with regard to food quality and safety. Nanotechnology has shown prospects in packaging and quality assurance of food products in order to minimize the ecological impact
in the environment, and provision of healthy foods to consumers [2]. The fabrication,
characterization, and electrochemical modeling of CNT-enzyme field effect acetylcholine biosensor has been conducted [248]. An amperometric biosensor with efficient
performance on novel spectrum composed of CNTs/zinc phthalocyanine and a conductive polymer has been constructed. The constructed biosensors underwent testing
on beverages and revealed efficient detection of glucose [249, 170].
Nanotechnology can be utilized to effect protection of packaged food products from
oxygen, moisture, antimicrobial and antifouling, spoilage detection, and monitoring of
storage conditions. TiO2 as food additive has been confirmed to be nontoxic to humans,
and can be applied to food packaging due to its function as food preservative. The
major challenges for cellulose nanofibers include their capability, sustainability, and
hindrances in food packaging [250]. Studies have revealed that nano-diamonds possess
antibacterial and anti-inflammatory properties and hold potentials for food packaging
application [171]. Nanodiamonds can be utilized as food additives and biosensors in
packaging to enhance protection of food products from spoilage by microbes and
toxins. Particles of nanodiamond in food packaging have been revealed to enhance
durability, flexibility, humidity, and temperature resistance, while also enhancing antimicrobial and anaerobic conditions [251]. The general issues notable in nanotechnology
and food packaging include its potential negative impact on human health, its adverse
environmental effects in the short and long run, and specific rules and regulations with
respect to nanomaterials.
The future of food packaging is focused on intelligent and robotic technologies.
Intelligent food packaging strategies have revealed potentials of detecting, sensing, and
recording variations in food products, their packaging, and environmental impact to
maintain quality of food. These future systems meet the demands of traditional food
packaging, and can refocus them into future advancement. These requirements include
protection of food, package communication, food consumer convenience, and food-containment. Presently, intelligent and robotic technologies in food packaging which are
available are still relatively evolving, such as the cradle-to-cradle and cradle-to-grave
sustainable intelligent food packaging systems. However, these novel technologies need
to be examined for their properties, hurdles, benefits, and adverse effects on food qualities.
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Moreover, it is expected that intelligent and robotic techniques and their utilization in food packaging will give better insight into better control and monitoring on
food quality, and safer and superior food qualities. Anti-counterfeiting and anticontamination sensors are areas of application of intelligent and robotic technologies in food packaging [252]. Thus, nanotechnology can operate in combination
with intelligent and robotic technologies in food packaging to attain the aim of
meeting consumers’ standards for a healthier and safer food product. The inclusion
of nano-devices and nano-sensors into food and beverage products offers anticounterfeiting and more secure attributes in warning and reminding applications
for consumers.
Hence, utilization of these technologies in food packaging has shown potentials of
enhancing food products reliability while increasing the confidence of consumers’
relative to food quality and safety in the future. Currently, developing intelligent tools
for food packaging are available in form of inks, tags, dots, and labels which offer
various functions aimed at improving food qualities and safety [12]. Sensors, nonsensors, and indicators of food standard and quality components can be combined and
incorporated into packaging to control food condition and preinform consumers about
food freshness and deterioration [242].
Nanotechnology utilization in food monitoring minimizes food-borne infections,
reduces food waste, and minimizes food product deterioration and spoilage. A notable
issue in these emerging technologies is the intricacies involved in intelligent and robotic
strategies and can potentially be amended through combination of varying components
involved in food monitoring and control to enable simplification of the devices and
materials utilized.
L-glutamate is amongst the essential 20 amino acids used by all organisms. Due to its
vital function in clinical applications and in food processing industries, amino acid
detection in food, and human serum are very imperative. Hence, research into glutamate monitoring has significantly escalated in previous decades, simultaneously with
the demand for improved sensor performance. Some vital factors in combination with
selectivity are the strategy on electrode fabrication. Thus, the importance of fabricating
high performing sensors exhibiting appropriate attributes such as sensitivity, responsetime, stability, biocompatibility, and reproducibility is imperative. Thus, a comprehensive micro- and nanostructure electrochemical sensor audit for glutamate detection has
been recently conducted.
5.3. Enzyme immobilization mechanisms
In previous decades, immobilization of enzymes has been in consideration for utilization in packaging applications [253]. Inclusion of enzymes such as lactase or cholesterol
reductase in packaging has resulted in food product value enhancement and offered
solution to consumer needs in enzyme-related health challenges [254].
On immobilization in varying bespoke carriers, enzymes show enhanced stability to
temperature and pH, improved hindrance to proteases and other denaturing compounds, in addition to suitable environment for their continual utilization or controlled
release [254]. Enzymes are broadly utilized in the food industry for numerous applications. In some instances, direct utilization of enzymes can be limited by influence of
COMPOSITE INTERFACES
43
processing conditions and compounds capable of hindering their action, which result in
short operational life or inactivation.
Nanoscale enzyme immobilization systems strongly improve performance, because of
their capability to enlarge available surface contact area while modifying the mass transfer [255]. Numerous materials have been developed to work in conjunction with biomolecules. Inorganic materials such as clays have a high affinity for protein adsorption, and
have been reported to be efficient enzyme carriers [256]. Hence, in future, new approaches
are expected to improve enzyme adsorption of clays incorporated into polymers, so as to
enable controlled release of enzyme molecules is expected. In a study, glucose oxidase (GO)
was immobilized onto poly (aniline-co-fluoroaniline) films [257]. nSiO2 underwent modification to immobilize glutamate dehydrogenase and lactate dehydrogenase. The enzymes
immobilized revealed excellent activity, facilitating the modification of nSiO2 for potential
utilization in biosensing applications. Numerous methods can be applied in the production
of enzyme immobilization films. In a study, layer-by-layer (LbL) assembling was utilized in
deriving a multilayer polypeptide antimicrobial nanofilm composed of positively charged
layers of egg white lysozyme, a chicken-derived enzyme specifically utilized as a food
preservative and negatively charged layering of poly(L-glutamic acid) [258]. These
nanofilms effectively inhibited the growth of Micrococcus luteus. This study revealed
effective controlling of the release rate of lisozyme through adjustment of the amount of
film layering. In another study, GO underwent successful immobilization in chitosan films
via LbL mechanism.
The activity of the enzyme was reportedly similar to a homogeneous solution, which
confirm suitability of LbL method of GO immobilization, with potential utilization in
varying system which entails catalysis such as biosensors. In comparison with established composites, PNC offer drastic variations in numerous properties at very low
inclusions especially at 2 vol% inclusion of nanofillers such as exfoliated nano-silicate
layers and CNTs [259].
However, the superior properties conferred by the inclusion of nanofillers can only
be attained through uniform dispersion of nanofillers and excellent interfacial adhesion
existing between the nanofillers and the polymer matrix. The concept of nanocomposites presents a stimulating route for creating new and innovative materials, also in the
area of natural polymers. Materials with a large variety of properties have been realized,
and even more are due to be realized.
The nanocomposite materials obtained by mixing natural polymers and sheets of
crystalline solid layered (clays or layered double hydroxides (LDHs)) offer a great
variety of property profiles. They are even able to compete, both in price and in
performance, with synthetic polymeric materials in packaging. In spite of the great
possibilities existing for packaging in bio-based nanocomposites materials, the future
scenario is difficult to predict. At this stage, we can only imagine that simple traditional
packing will be replaced with multifunctional intelligent packaging.
LDHs consist of a group of inorganic solid particles exhibiting structural closeness to
brucite Mg (OH)2. They are elaborately utilized in large scope researches including
catalysis, biomedical applications, nuclear waste storage/treatment, water treatment,
composites, and so on. LDHs provide a large surface area and a huge boundary with
the polymer, which influence the properties of the materials. Thus, presently, LDHs are
attracting greater interests as reinforcement material for the synthesis of PNC. Thus,
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nowadays, biopolymer researches in nanocomposite fabrication are on the increase due
to their relative versatility, eco-benign tendencies, and low cost. Thus in a recent study,
LDH-reinforced polymer bio-nanocomposites for packaging applications were reviewed
and efficiency in use as effective food packaging materials was elucidated [121].
The next generation of packaging materials is expected to meet up with the requirements
of preserving fruit, vegetable, beverage, wine, and other foods. By adding appropriate
nanoparticles, it will be possible to produce packages with stronger mechanical, barrier,
and thermal performance. However, in order to preserve food safety, nanostructured
materials will prevent the invasion of bacteria and microorganisms.
Numerous studies based on bioactive plant extracts or essential oils (EOs) inclusion
into polymers to inculcate antimicrobial functionality have been conducted. EOs provide
special combinations of antimicrobial activity from a natural source, generally perceived
as safe in the US, and a volatile attribute. On the other hand, their volatility also offers a
major challenge in their inclusion in polymers via conventional high-temperature processing techniques. Here, antimicrobial PP cast films have been fabricated through inclusion
of carvacrol (a model EO) or carvacrol, incorporated into halloysite nanotubes (HNTs),
via melt blending [65]. Studies revealed strong molecular interactions between PP and
carvacrol which reduced the loss of highly volatile EO during high-temperature polymer
processing. This enable semi-industrial scale production.
The fabricated films exhibited significant antimicrobial properties against model
microorganisms (E. coli and Alternaria alternata). The PP/(HNTs-carvacrol) nanocomposite films, with inclusion of carvacrol-loaded HNTs, exhibited elevated level of
crystallinity, superior mechanical properties, and prolonged release of carvacrol, when
compared with PP/carvacrol blends. These properties were attributed to HNTs influence in these nanocomposites and their influence on PP/carvacrol films as elucidated in
Figure 12.
Nowadays, the largest part of materials used in packaging industries is produced
from fossil fuels and is practically un-degradable. For this, packaging materials for
foodstuff, like any other short-term storage packaging material, represent a serious
global environmental problem [14].
PLA has been reactively compounded with thermoplastic cassava starch (TPCS) and
functionalized using graphene (GRH) nanoplatelets via twin-screw extruder, and films
were fabricated using cast-film extrusion [260]. SEM images revealed a nonuniform
dispersion of GRH nanoplatelets in the matrix. Transmittance of the reactive blend films
reduced as result of the TPCS phase. Values derived for the reactive blends revealed ~20%
transmittance. PLA-GRH and PLA-g-TPCS-GRH revealed a minimization of the OP
coefficient with respect to PLA of about 35% and 50%, respectively. Figure 13(a, and b)
reveals a SEM and AFM image of GRH dispersion in PLA respectively [260].
The characterization of NC extracted from the Moroccan Alfa plant (Stipa tenacissima L.) has been conducted. These Alfa cellulosic NPs were utilized as fillers in the
preparation of bio-nanocomposite films utilizing carboxymethyl cellulose as matrix via
casting/evaporation technique [261]. The properties of the derived bio-nanocomposite
films improved tensile modulus and tensile strength of CMC film by 60% and 47%,
respectively, in the bio-nanocomposite films with 10 wt% of NC, and decrease by 8.6%
for WVP with equal inclusion of NC. Summarily, NC derived from the Moroccan Alfa
fibers can be utilized as reinforcement fillers for the preparation of bio-nanocomposites,
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45
Figure 12. Cryo-fractured cross-sectional high-resolution scanning electron microscope (HR-SEM)
images of (a) pristine PP and (b) PP/(HNTs-carvacrol) films. Various HNTs are inked with arrows for
clarification. The HNTs are evenly distributed within the PP matrix. The inset reveals a micrograph,
showing HNTs extending from the PP matrix. The HNTs exhibit peculiar morphology of cylindrical
tubes, with an exterior diameter of up to 100 nm [65]. (c) Antimicrobial influence of pristine PP, PP/
carvacrol, and PP/(HNTs-carvacrol) films exhibited in the micro-atmosphere diffusion assays, i.e.,
without direct contact between the studied films and the microbial cultures. Top panel: Petri dishes
containing the E. coli after incubation with the films for 12 h at 37 C (the margins of the inhibition
zone are marked for clarity). Bottom panel: Petri dishes containing A. alternata following 7 days of
incubation at 25 C in the dark [65].
Figure 13. (A) SEM images of film samples showing the polymer domains and distribution of GRH
nanoplatelets: (a) PLA-c; (b) PLA-g-TPCS; (c) PLA-GRH (1000); (d) PLA-g-TPCS-GRH (1000); (e) PLAGRH (3000); and (f) PLA-g-TPCS-GRH (3000). (B) AFM images of films: (a) PLA-c; (b) PLA-g-TPCS; (c)
PLA-GRH; and (d) PLA-g-TPCS-GRH [260].
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exhibiting high potential for development of completely biodegradable food packaging
materials as elucidated by Figure 14(a, and b) respectively.
A grand intent on extension of shelf life and enhancement of food quality while
reducing packaging waste has encouraged the exploration of new bio-based packaging
materials, such as edible and biodegradable films from renewable resources. The use of
these materials, due to their biodegradable nature, could at least to some extent solve the
waste problem. However, like conventional packaging, bio-based packaging must serve a
number of important functions, including containment and protection of food, maintaining its sensory quality and safety, and communicating information to consumers.
AgNPs have been used in combination with minerals such as zeolites and gold NPs.
Results revealed a synergic influence against some microorganisms [38]. The synergism of
silver–zeolites and silver–gold combinations revealed a larger antibacterial influence in
comparison with silver used alone, though presently it has not been commercialized [5].
The fabricated composites in form of films were attained by compression molding as
shown in Figure 15(a). The influence of varying AgNPs content (0, 0.5, 1, and 2 wt%) on
attributes of LDPE and the antimicrobial efficiency of the composite against DH5 E. coli
were investigated as elucidated in results in Figure 16. The availability of AgNPs apparently did not influence the surface energy and thermal attributes of the materials. Results
revealed that these materials may prospectively be commercially utilized in producing
antimicrobial polymers with potential use in food and health sectors [5].
Unfortunately for natural polymers, thus far, use of biodegradable films for food
packaging has been strongly limited due to the poor barrier properties and weak
mechanical properties they exhibit. For this reason, natural polymers are frequently
Figure 14. (A) The AFM images show an area of 1.6 × 1.6 mm. AFM images of (a) NC height and
amplitude and (b) tapping mode. (B) Pictures of films of (a) neat CMC and CN/CMC nanocomposite
films, (b) NC 3%, (c) NC 5%, and (d) NC 10% [261].
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47
Figure 15. (a) Photographic image of the specimen cut in circular disks within diameter of 1 cm; SEM
micrographic images derived using BSE detector for: (b) PE-0.5% Ag; (c) PE-1% Ag; (d) PE-2% Ag and
(e) magnification of (c) to show the size of the domains (where PE represents polyethylene) [5].
Figure 16. (A). Characteristic (a) TGA curves and (b) DTGA curves of LDPE and LDPE/Ag nanocomposites. (B) SEM micrographs obtained at 1000× for PE-Ground; (C) PE-0.5% Ag; SEM micrographs
obtained at 2500× for: (D) PE-Ground; (E) PE-Milled; (F) PE-0.5% Ag; (G) PE-1% Ag [5].
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blended with other synthetic polymers or, less frequently, chemically modified with the
aim of extending their applications in more special or peculiar areas [262].
Great attention has recently emerged toward hybrid organic–inorganic systems
especially those having layered silicates dispersed at a nanometric level in polymeric
matrix [263]. Such nano-hybrid composites possess very unusual properties, very
different from their microscale counterparts. They often exhibit improved mechanical
and oxidation stability, reduced solvent uptake, self-extinguishing attributes, and, eventually, tunable biodegradability. The application of nanocomposites promises to expand
the use of edible and biodegradable films. It will assist in reducing packaging waste
associated with processed foods and overall shelf life.
6. Advancements of PNC in electronic packaging
Nowadays, there has been escalating interest in the evolvement of electronic circuits on
flexible materials to satiate the growing quest for lower-cost, broad-area, flexible, and lightweight devices, such as e-papers, connectors, roll-up-displays, and keyboards [264].
Nanocomposite materials and organic/polymers have aroused loads of interests for development of vast area, mechanically flexible electronic devices. These substrates are versatily
desired as they provide varying benefits such as ease of processing, good compatibility with
varying substrates, and huge privilege for structural modifications [265]. Remarkable
improvement has been recorded in organic thin-film transistors, solar cells, and organic
light-emitting diodes for flat-panel displays utilized in mass production [266]. Escalating
demand to develop advanced large-scale novel materials capable of satisfying the growing
quest for compact, high-speed performing, and flexible materials for microelectronic
devices has aroused. Thus, PNC have been utilized in printable and flexible technologies
for electronic packaging. Moreover, printable techniques such as screen, ink-jet, and microcontact printing enable a fully inclusive, non-contacting deposition technique appropriate
for flexible production [267]. The electronic utilization of printable, high-performing
nanocomposite materials including conductive and nonconductive adhesives such as
low-loss and interlayer dielectrics, and submerged passives such as capacitors, resistors,
and circuits is further schematically elucidated in Figure 17.
Notably, studies into printable optic and magnetic-based active polymeric nanocomposite materials for formation of devices such as inductors, embedded-lasers, and
optical inter-connectors have been undertaken. In fabricating some nanocomposites,
a polymeric matrix with inclusion of a range of metallic and ceramic fillers with particle
size in the range of 10 nm–10 μm has been undertaken [268,269]. The inclusion of
varying fillers into the polymer matrix facilitates control of the general electrical
properties of the composites. In the study of antimicrobial nanocomposites fabricated
from MMT/Ag+/quaternary ammonium nitrate, improved antimicrobial attributes
were attained [85]. This was attributed to synergistic interaction of the varying components which were uniformly distributed as revealed by TEM images in Figure 18(a,b)
and SEM images as shown in Figure 18(c,d).
A new class of PNC exhibiting high dielectric constant such as BaTiO3-epoxy
nanocomposite has been utilized in the fabrication of thin film included capacitors.
Nanocomposites are also good for resistor applications because variable resistor materials are feasibly formed by varying the ratio of the metal insulator. Elevated
COMPOSITE INTERFACES
49
Figure 17. Summary of some potential nanocomposites uses in microelectronics.
Figure 18. (a) TEM of Ag-MMT, (b) TEM and EDS of Ag-OMMT, (c) SEM micrograph of MMT, and (d)
Ag-MMT [85].
temperature/pressure lamination has been utilized in including capacitors in multiple
layering printed circuit boards. Nanocomposites with printability have shown prospective applicability for microelectronics.
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C. I. IDUMAH ET AL.
7. Surface modification effect on interfacial adhesion of PNC films
The fundamentals of composite materials are function of their inherent interfacial
characteristics [18]. The physical behavior of composites is posited via the rule of
mixtures, expressing the average physical attributes of the filler and the matrix [212].
The interior adhesive strength of composites interface can be improved through
enhancement of the strength of bonding strength via inclusion of a trace amount of
substrates at the interface [30]. The composites interface constitutes the fundamentals
of composite structures [35]. There is a notable variation between the physical, chemical, and mechanical attributes of the reinforcement fibers and the polymeric matrices
[18–23]. Hence, on combination of materials, the interfacial behavior between the
materials that are not similar can exhibit high impact on the composites mechanical
behavior [24–26]. Though, composite physical behavior is often defined by the rule of
mixtures, in certain practical conditions, the rule of mixtures does not apply. This
results when an exterior energy applied to the composite film is transferred from the
polymer to the filler, thereby impacting on the accruable physical behavior of the
interface existing between them, instead of the intrinsic behavior of both filler and
the polymer matrix [27]. Additionally, each matrix or filler creates strong interior
chemical bonding, while their interface creates a poor physical bonding. Thus, an
applied external force is function of the exterior physical bonding [25]. The behavior
of the natural fiber polymer composites (NFPC) is function of varying factors, including
fibrous microfibrillar angle, defects, structure, physical attributes, chemical constitution,
cell sizes, mechanical attributes, and the interaction occurring between the natural fiber
(NF) and polymer matrix [18–26]. The major parameters occurring in development of
NFPC include (1) fiber surface adhering behavior, (2) fiber thermal stability, and (3)
degree of distribution of the fibers in thermoplastic composites [23]. The polarity
affinity of NF causes incompatible challenges with varying polymers. The hydrophilic
or polar identities of NFs result in composites exhibiting poor interfacial behavior.
Thus, varying surface chemical treatments or pretreatments are conducted to enhance
adherence or interfacial bonding between polymeric matrices and NFs [213].
Premodification of NF results in cleansed fiber surface, surface chemical modification,
reduction in moisture absorption rate, and increment of external roughness. The
inclusion of NFs as reinforcement results in notable variations in thermal stability of
polymeric matrix.
Polymeric matrix reinforcement using NPs, such as CNTs, MMT [115], or intercalation layering in formation of nanocomposites, is an enchanting area of research.
Layered/PNC are generally categorized into intercalated, flocculated, and exfoliated
nanocomposites [18–25]. A very broad matrix interfacial surface or interphase is
exhibited by nanocomposites, revealing attributes quite dissimilar from the bulk polymer as a result of the elevated specific surface area of the nanofiller.
The dimension of cellulose nano-reinforcements, effect the behavior of their nanocomposites. NC can undergo extraction via enzymatic modifications, tempo-oxidation
and chemical treatments, while CNC undergo extraction through mainly acidolysis with
sulfuric acid [74–76]. Nanocrystals distribution in nil-aqueous media is also feasible via
surfactants or chemical grafting. Polysaccharide nanocrystals are coated with reactive
hydroxyl entities, offering broad chemical treatment via grafting carrying a reactive
COMPOSITE INTERFACES
51
end-group and elongated compatibilization tail [30]. The surface chemical modification
of the cellulose biofibers results in enhanced interfacial adhesion between fibers and
matrix, forming improved mechanical and thermal stabilizing behavior.
Generally, fibers in bonding with matrices in fiber-filled composites function to carry
load and restrain crack initiation and propagation when composites are subjected to
varying loads. Hence, the matrices strength and interfacial adherence between fibers
and matrices mainly determine the composites end properties. Thus, interfacial adherence between fibers and matrices determines properties of composite laminates, peculiarly mechanical properties. Therefore, investigations into improving interfacial
adhesion between fibers and matrices have been conducted recently. The design and
fabrication of fiber-filled composites with improved interfacial adherence has been
recently conducted [270]. In this investigation, phthalonitrile with inclusion of benzoxazine (BA-ph) was used as the resin matrix in combination with glass fiber (GF) to
fabricate filled composite laminates at lower temperature (200 C). Poly(arylene-ethernitrile) (PEN) was used in modification of the GF and BA-ph matrix [270]. Figure 19
shows FE-SEM images of various composite laminates, while Figure 20 is a proposed
mechanism of enhanced interfacial adherence of the composite laminates.
7.1. CNTs/polymer composite interfaces
The ultimate aim of CNT inclusion is attainment of appropriate distribution in polymer
matrices and properties improvement. As a result of inherent high shearing rates, CNTs
Figure 19. FESEM image of varying composite laminates: (a) BA-ph; (b) BA-ph/PEN blends with 20 wt
% PEN constitution; (c) zoomed image of (b,d) BA-ph/PEN blends composed of 40 wt% PEN; the
arrows depict the gaps between matrix and GF in Figure 19(a), in addition to adhesion properties in
Figure 19(b–d); the cycles depict GF rough surface and the smooth surface of the matrix; the
rectangles represent the zoomed image of the adhering attributes of the composites in a specific
zone [270].
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C. I. IDUMAH ET AL.
Figure 20. Proposed mechanism of enhanced interfacial adherence of the composite laminates [270].
dispersion in thermosetting matrices can undergo improvement devoid of any surface
modification [91]. CNT distribution can be enhanced through functionalization of the
CNTs surface [170]. These modifications enhance interfacial interactions with the
matrix. Three routes are feasible via chemical functionalization of covalent bonds
[171]. Varying techniques abound for chemical functionalization of CNTs for introduction of carboxylic acid groups on the surface. This UV/O3 treatment enhances
distribution and interfacial bonding of CNTs to the epoxy matrix. Surface functionalization of CNT can occur with amines [170–172]. The amine can form covalent
bonding with the epoxy matrix; functionalization using silanes [173]. CNTs undergo
oxidation on exposure to UV, in the presence of ozone, which reduces to hybrid
aluminum-lithium solution followed by silanization. Silane functionalization enhances
CNTs distribution in matrix. CNTs distribution in a thermosetting matrix can be
enhanced via non-covalent physical treatments, with the benefit of not damaging
CNT, or exposure to defects. CNTs can also be functionalized through surfactant
inclusion [91,170]. The physical adsorption of surfactant on CNTs surface reduces its
surface tension, thereby hindering agglomerates formation [170].
Studies of the surface sizing modified MWCNTs and its influence on the wettability,
interfacial interaction, and flexural properties of MWCNT/epoxy nanocomposites have
been undertaken. The fractured surfaces of pristine resin and nanocomposites composed
COMPOSITE INTERFACES
53
of MWCNT-NH 2, MWCNT-BuGE, and MWCNT-BeGE underwent comparison via
SEM, as shown in Figure 21. Small particles of MWCNT agglomerates were visible from
the specimen composed of MWCNT-NH 2 (Figure 21(b), inset), while these aggregates
were almost not seen in the sample with MWCNT-BuGE (Figure 21(c), inset) and
MWCNT-BeGE (Figure 21(d), inset). This result revealed that the surface sizing modified
MWCNTs further enhanced the distribution effect of MWCNT-NH 2 in the matrix. The
surface sizing decreased the van der Waals (vdW) force between the MWCNTs and
improved the CI with epoxy matrix, resulting in the effective de-bundling and even
distribution of MWCNTs in the nanocomposites.
Figure 22 shows the G-band intensity dispersion across the scanned zone of cured
DGEBA/DDM nanocomposites filled MWCNT-NH 2, MWCNT-BuGE, and
MWCNT-BeGE devoid or with 1% bending load at ambient temperature. No notable
variation in the G-band frequency (~1582.0) among the MWCNT-NH 2, MWCNTBuGE, and MWCNT-BeGE was observed prior to external stress application.
However, on application of the 1% bending load, the G-band frequency of
MWCNT-BuGE (1596.2) and MWCNT-BeGE (1598.4) moved to elevated wave
number than that of MWCNT-NH 2 (1594.6), implying effective stress transfer
from matrix to surface sizing-treated MWCNTs at their interfaces. The G-band
frequency of MWCNT-BeGE/epoxy nanocomposites was superior in comparison
with MWCNT-BuGE/epoxy nanocomposites as a result of the stronger interfacial
interaction within the MWCNT-BeGE and the epoxy matrix.
It is well established that inclusion of NPs into polymer composite films can
regularly vary the structure, dynamics, and mechanical properties. However, these
property variations result from inclusion of NPs depending on numerous factors such
as interactions between polymer/NP, molecular weight, and polymer chain topology,
Figure 21. The fracture surfaces of neat resin and nanocomposites containing MWCNT-NH 2,
MWCNT-BuGE, and MWCNT-BeGE.
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C. I. IDUMAH ET AL.
Figure 22. G-band intensity dispersion across the scanned zone of cured DGEBA/DDM nanocomposites filled with MWCNT-NH 2, MWCNT-BuGE, and MWCNT-BeGE.
size of polymer, shape of NP, and so on. Simultaneously, these factors are consistently
intercorrelated and they vary between different systems. Thus, microscopic mechanisms
which control PNC films are expected to change between systems and are distant from
been widely investigated.
7.2. Graphene/PNC interface
Poor distribution network and weak interfacial bonding in matrix hinder graphene
usage as reinforcement for composites [35–37]. The weak graphene distribution in
composites is caused by its inherent lack of solubility in matrices, vdW forces, and
occurrence of stacking in graphene layers. Graphene is typically prone to agglomeration
and irreversible precipitation in numerous matrices [89,90]. The poor strength of
bonding between graphene and varying matrices is mainly caused by poor surface
activity of graphene, which posits graphene difficulty in bonding with matrice interfaces
[115,155]. Hence, it has become imperative to overcome the poor distribution and poor
adherence of graphene in the matrices of polymer composites. In a bid to find panacea
to this challenge, it has become essential to investigate the distribution techniques and
mechanisms of graphene. Three modes of graphene distribution techniques are recognized vis-a-vis physical distribution, covalent bonding, and non-covalent bonding
techniques [158,164,173]. Physical distribution technique involves mechanically dispersing aggregated graphene plates. The wide range of application of graphene PNC is
attributable to its excellent physical and chemical behavior.
COMPOSITE INTERFACES
55
7.3. Nanoclay and silica-based PNC interfaces
In previous decades, organic/inorganic PNC composed of clay-layered silicates are used
as good alternative for inorganic phase of PNC. The interlayering distance is estimated to
about 1 nm [153]. The virgin-layered structure can undergo further exfoliation forming
NPs within the polymer matrix [159]. Generally, two fundamental microstructures are
developed through nano-silicate fillers usage: (1) mechanism where layerings of silicate
undergo exfoliation or total delamination and disorderliness and (2) partial separation of
polymer chains, with stable alignment of structure, i.e., proper maintenance of the silicate
layering [11,85,154]. Effective distribution of clay sheets results in a large property
enhancement as the effect of nanostructure is more notable in exfoliated nanocomposite
than in the intercalated architecture. Excellent nanocomposite formation is function of a
nanoclay precursor which efficiently intercalates, with a compounding process which
uniformly distributes and completely delaminates/exfoliates nanoclay in the polymeric
matrix [175]. The level of delamination and dispersion is influenced by the type of clay
chemical modification and extruder/screw design in use [176]. At the initial phase of
compounding, organoclay NPs easily undergo disintegration into tactoids or stacks of
intercalated sheets, which is subsequently followed by a highly delaminated or exfoliated
phase. Two distribution mechanisms that are recognized include shearing of NPs and
peeling of nanoplatelets or sheets as schematically elucidated in Figure 23. The initial
mechanism is dependent on the compounding design and high shearing rate, whereas the
later is function of the diffusion of the polymer chain into the vicinity of the interlayering.
The efficiency of the peeling mechanism is function of the degree of compatibility of
organic intercalation layering with effective penetration of polymer chain within the
intercalated microstructure [178–181].
Furthermore, the clay arrangement also influences the extent of exfoliation attained,
though this depends on the dimension and orientation of the clay sheet. Thus, it might
be easier for peeling of the layering during shearing to occur when aligned in direction
of molten polymer flow during the melt processing stages due to clay extensive aspect
ratio as depicted in Figure 24.
Figure 23. Dispersion mechanism of organoclay nanoparticles in polymer matrices.
56
C. I. IDUMAH ET AL.
Figure 24. Exfoliation of clay nanosheets because of nanosheet dimension and orientation during
melt mixing.
A surfactant is utilized in modifying the polymer or the filler so as to overcome the
immiscibility challenge occurring due to the polymer hydrophobicity and the clay
hydrophilicity [182]. Organic species can be included into the interlayer gallery as
neutral molecules, cations, or anions for anionic clays [183]. The intercalation procedures are attained via solid–liquid, solid–gas, and solid–solid interaction between clay
flour and organic material in solid phase [187]. Solid–solid interaction relies on efficient
diffusion and penetration of organic species from the exterior surfaces of visiting solid
into the interlayer gallery [189]. This implies that intercalated/exfoliated co-existing
microstructure relies on the clay composition as schematically elucidated in Figure 25.
A very vital aspect of nanocomposites fabrication involves particle surface modification. A fundamental mechanism in compatibilizing phase-isolated polymeric blends
Figure 25. Clay sheets distribution in polymer matrix: exfoliated (a) intercalated (low concentration),
(b) high intercalation and (c) polymer nanocomposite.
COMPOSITE INTERFACES
57
involves reduction of the interfacial tension between the phases and inhibition of
particles agglomeration during melt mixing [191]. The interactions occurring between
the reactant groups of the polymer and the NPs are dependent on the polymer chemical
structure, and the NP surface charge. These interactions are categorized into covalent
bonds, ionic bonds, and chiral bonds.
7.4. Gas diffusion behavior
The solvent and gas diffusion attributes of polymers can undergo modification via
nanofiller usage, especially when nanoplates are utilized [192]. This factor is very vital
in some applications especially food packaging. The structure attained by the polymer
on utilizing nanoplates results in increased distance of gaseous movement within the
plates. This distance is ascribed as the ‘tortuosity’ factor [115]. It is available for
nanocomposites using nanoclays, and depends on distribution, diffusion, exfoliation,
and plates’ orientation. Improved barrier behavior of gas transfer is related to the
parallel alignment of organo-modified nanoclay sheets, and thus requires a high level
of exfoliation [155]. This behavior will result in formation of novel food packaging
materials, as diffusion of oxygen is a determinant factor for food storage.
8. Conclusion
Nanocomposites concept has technologically introduced novelty in fabrication of a new
class of innovative polymeric materials. These have facilitated the fabrication of varieties of polymeric nanocomposites possessing versatile, interesting, and superior properties including barrier, mechanical, electrical, and thermal properties. Additionally,
some of these materials have attained fire inhibition, thermomechanical attributes, and
heat deflection while maintaining varying polymer matrix transparency. These materials
have also demonstrated capability of competing, relative to costing and efficiency in
various applications especially in packaging. With regard to the great future prospects
of PNC packaging materials, this is favorably anticipated especially relative to the
replacement of simple packaging systems with high-tech intelligent packaging systems.
The use of biopolymers as packaging films in the food sector has incurred challenges
due to their high cost and inferior performances when compared with synthetic
polymeric materials. Great potentials abound for growth in the applications of nanocomposites in biodegradable and edible packaging films. However, varying NPs have
included active and smart prospects in food packaging materials, such as antimicrobial
and oxygen-scavenging abilities, enzyme immobilization, and exposure to some degradative factors.
Cellulose is a very interesting natural polymer. A highly promising fraction of cellulose
is nanofibrillated cellulose widely utilized in numerous applications, with some deficiencies limiting its scope of application, such as agglomeration and compliance with hydrophobic polymeric matrices. A route of overcoming these challenges includes chemical
treatment of NFC, capable of offering novel functionalities to these materials. The
capability of controlling NFC depends mainly on the feasibility of modifying the interfacial adherence via enhancement of the interactions of the fiber matrix.
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C. I. IDUMAH ET AL.
Polymeric materials reinforcement via NPs has opened up a large window of
opportunities and improvement of modulus and composites strength through inclusion of low filler inclusion. The reinforcement degree is function of the type of
reinforcement, filler functional group, aspect ratio, filler amount, polymer behavior,
and processing technique. The nanofiller uniform distribution in the polymer and
high interaction between nanofiller and polymer are imperative to attaining better
reinforcement.
Graphene exhibits numerous physical and chemical attributes, enabling its versatile
applications in numerous fields. Nevertheless, graphene inferior dispersion and its
permanent agglomeration challenges hamper further graphene usage because excellent
distribution and strong interfacial bonding can notably enhance the physical and
chemical behavior of the composites, while also enhancing the efficiency of production
and range of feasible composites applications especially in the packaging sector. Lack of
functionalization causes ineffective dispersion of clays and CNTs in polymer matrices,
due to formation of microscale agglomeration as result of their inferior attraction to
polymers and higher tendency toward agglomeration. Thus, the interfacial adhesion
between clays and/or CNTs and polymer matrices is highly enhanced via filler functionalization, which enables uniform nanoscale distribution of the reinforcing fillers
within the matrices. Finally, the degree of interfacial adherence of the components
making up PNC films for packaging applications is critical to high efficiency and
prolonged shelf life and future dynamic research at achieving high interfacial bonding
in composites are essential.
Acknowledgments
Acknowledgement is given to Universiti Teknologi Malaysia; Manchester University, England,
United Kingdom; Federal University of Technology Owerri; and Ebonyi State University,
Abakaliki, Nigeria for knowledge and quest for academic excellence.
Disclosure statement
No potential conflict of interest was reported by the authors.
ORCID
C. I. Idumah
http://orcid.org/0000-0003-1014-6751
References
[1] Bajracharya S, Sharma M, Mohanakrishna G, et al. An overview on emerging bioelectrochemical systems (BESs): technology for sustainable electricity waste remediation, resource
recovery, chemical production and beyond. Renew Energy. 2016;98:153–170.
[2] Neethirajan S, Ragavan V, Weng X, et al. Biosensors for sustainable food engineering:
challenges and perspectives. Biosensors (Basel). 2018;8:23.
[3] Firestein K, Leybo D, Steinman EA, et al. BN/Ag hybrid nanomaterials with petal-like
surfaces as catalysts and antibacterial agents. Beilstein J Nanotechnol. 2018;9:250–261.
COMPOSITE INTERFACES
59
[4] Bott J, Störmer A, Albers P. Investigation into the release of nanomaterials from can
coatings into food. Food Packaging Shelf. 2018;16:112–121.
[5] Olmos D, Pontes-Quero G, Corral A, et al. Preparation and characterization of antimicrobial films based on LDPE/Ag nanoparticles with potential uses in food and health
industries. Nanomaterials. 2018;8:60.
[6] Radusin T, Ristic I, Pilic B, et al. Antimicrobial nanomaterials for food packaging applications. Food Feed Res. 2016;43:119–126.
[7] Silvestre C, Duraccio D, Cimmino S. Food packaging based on polymer nanomaterials.
Prog Polym Sci. 2018;36:1766–1782.
[8] Dasgupta N, Ranjan S. Nanotechnology in food packaging. In: Dasgupta N, Ranjan S,
Lichtfouse E, editors. An introduction to food grade nanoemulsions. Environmental
chemistry for a sustainable world. Singapore: Springer; 2018. p. 129–150.
[9] Govekar S, Kumar R, Suresh R, et al. Nanotechnology to sustain a clean environment. In:
Sridharan K, editor. Emerging trends of nanotechnology in environment and sustainability. springerbriefs in environmental science. Cham: Springer; 2018. p. 3–11.
[10] Kasi VH, Thomas NR, Amaranath G. Nanotechnology in the food industry—and the
benefits and improvements in food processing and packaging brought about by it. In:
Sridharan K, editor. Emerging trends of nanotechnology in environment and sustainability. springer briefs in environmental science. Cham: Springer; 2018. p. 21–25.
[11] Kumar M, Panjagari N, Kanade P, et al. Sodium caseinate-starch-modified montmorillonite based biodegradable film: laboratory food extruder assisted exfoliation and characterization. Food Packaging Shelf. 2018;15:17–27.
[12] Aghamiri Z, Mohsennia M, Rafiee-Pour H. Immobilization of cytochrome c and its
application as electrochemical biosensors. Talanta. 2018;176:195–207.
[13] Caon T, Martelli S, Fakhour F. New trends in the food industry: application of nanosensors in food packaging. Nanobiosensors. 2017;773–804.
[14] Kozitsina A, Svalova T, Malysheva N, et al. Sensors based on bio and biomimetic receptors
in medical diagnostic environment and food. Biosensors (Basel). 2018;8:35.
[15] Idumah C, Hassan A, Affam A. A review of recent developments in flammability of
polymer nanocomposites. Rev Chem Eng. 2015;31:149–177.
[16] Idumah C, Hassan A. Characterization and preparation of conductive exfoliated graphene nanoplatelets kenaf fibre hybrid polypropylene composites. Syn Met.
2016;212:91–104.
[17] Idumah C, Hassan A. Recently emerging trends in thermal conductivity of polymer
nanocomposites. Rev Chem Eng. 2016;32:413–457.
[18] Idumah C, Hassan A. Emerging trends in flame retardancy of biofibers, biopolymers,
biocomposites, and bionanocomposites. Rev Chem Eng. 2015;32:115–148.
[19] Idumah C, Hassan A. Emerging trends in graphene carbon based polymer nanocomposites
and applications. Rev Chem Eng. 2016;32:223–264.
[20] Idumah C, Hassan A. Effect of exfoliated graphite nanoplatelets on thermal and heat
deflection properties of kenaf polypropylene hybrid nanocomposites. J Polym Eng.
2016;36:877–889.
[21] Idumah C, Hassan A. Emerging trends in eco-compliant, synergistic, and hybrid assembling of multifunctional polymeric bionanocomposites. Rev Chem Eng. 2016;32:305–361.
[22] Idumah C, Hassan A, Bourbigot S. Influence of exfoliated graphene nanoplatelets on flame
retardancy of kenaf flour polypropylene hybrid nanocomposites. J Anal Appl Pyrol.
2017;123:65–72.
[23] Idumah C, Hassan A. Hibiscus cannabinus fiber/PP based nano-biocomposites reinforced
with graphene nanoplatelets. J Nat Fibers. 2017;14:691–706.
[24] Idumah C, Hassan A, Ogbu J, et al. Recently emerging advancements in halloysite
nanotubes polymer nanocomposites. Compos Interfaces. 2018;1–74. DOI:10.1080/
09276440.2018.1534475
60
C. I. IDUMAH ET AL.
[25] Idumah C, Hassan A, Ogbu J, et al. Electrical, thermal and flammability properties of
conductive filler kenaf reinforced polymer nanocomposites. J Thermoplast Compos Mater.
2018;089270571880795. DOI:10.1177/0892705718807957
[26] Idumah C, Hassan A, Bourbigot S. Synergistic effect of exfoliated graphene nanoplatelets
and non-halogen flame retardants on flame retardancy and thermal properties of kenaf
flour-PP nanocomposites. J Therm Anal Calorim. 2018. DOI:10.1007/s10973-018-7833-3
[27] Popović S, Lazić V, Hromiš N, et al. Biopolymer packaging materials for food shelf-life
prolongation. Biopolymers for food design. In: Grumezescu AM, Holban AM, editors. A
volume in handbook of food bioengineering. Novi Sad, Serbia: Academic Press, University
of Novi Sad; 2018. p. 223–277.
[28] Ali Y, Jasim A, Mohammed A, et al. Polylactide/graphene oxide nanosheets/clove essential
oil composite films for potential food packaging applications. Int J Biol Macromol.
2018;107(Part):A: 194–203.
[29] Ariffin H, Norrrahim M, Yasim-Anuar T, et al. Oil palm biomass cellulose-fabricated
polylactic acid composites for packaging applications. In: Jawaid M, Swain S, editors.
Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 95–105.
[30] Alvarado N, Romero J, Torres A, et al. Supercritical impregnation of thymol in poly (lactic
acid) filled with electrospun poly (vinyl alcohol)-cellulose nanocrystals nanofibers: development an active food packaging material. J Food Eng. 2018;217:1–10.
[31] Andrade F, Buonocore G, Stanzione M, et al. Monitoring lipid oxidation in a processed
meat product packaged with nanocomposite poly (lactic acid) film. Eur Polym J.
2018;98:362–367.
[32] Ali A, Xie F, Yu L, et al. Preparation and characterization of starch-based composite films
reinfoced by polysaccharide-based crystals. Compos Part B-Eng. 2018;133:122–128.
[33] Altan A, Aytac Z, Uyar T. Carvacrol loaded electrospun fibrous films from zein and poly
(lactic acid) for active food packaging. Food Hydrocoll. 2018;81:48–59.
[34] Akbari A, Majumder M, Tehrani A, et al. (ed.) Springer materials polylactic acid (PLA)
carbon nanotube nanocomposites (handbook of polymer nanocomposites. Proces Perform
Appl. 2015; volume B [Cited 2018, April 15]. p. 283–297.
[35] Damari SP, Cullari L, Nadiv R, et al. Graphene-induced enhancement of water vapor
barrier in polymer nanocomposites. Compos B Eng. 2018;134:218–224.
[36] Díez-Pascual A, Sánchez J, Capilla R, et al. Recent developments in graphene/polymer
nanocomposites for application in polymer solar cells. Polymers. 2018;10:217.
[37] Gao Y, Picot O, Tu W, et al. Multilayer coextrusion of graphene polymer nanocomposites
with enhanced structural organization and properties. J Appl Polym Sci. 2018;135:46041.
[38] Palem R, Ganesh SD, Kronekova Z, et al. Green synthesis of silver nanoparticles and
biopolymer nanocomposites: a comparative study on physico-chemical, antimicrobial and
anticancer activity. Bull Mater Sci. 2018;41:55.
[39] Kaewklin P, Siripatrawan U, Suwanagu A, et al. Active packaging from chitosan-titanium
dioxide nanocomposite film for prolonging storage life of tomato fruit. Int J Biol
Macromol. 2018;112:523–529.
[40] Lavrov RV, Mironovich LM. A novel method for preparing a batch of silicate glasses using
sodium and potassium hydroxides. Glass Phys Chem. 2018;44:145.
[41] Iskhakova LD, Milovich FO, Erin D, et al. Phase Separation and crystallization of
phosphate–silicate glass cores of preforms of fiber optics. Glass Phys Chem.
2018;44:137–144.
[42] Chubraeva LI. Study of the physical properties of metallic glasses at cryogenic temperatures. Glass Phys Chem. 2018;44:123.
[43] Kuznetsova AS, Volkova AV, Ermakova LE, et al. Iron (III) ion adsorption on macroporous glass. Glass Phys Chem. 2018;44:41–46.
[44] EcoFocus Worldwide. [Cited 16 April 2019]. Available from: ecofocusworldwide.com
[45] Petric D, Vusic D, Gecek R. Paperboard: from the production to the final use. Tehnicki
Glasnik. 2012;6:219–227.
COMPOSITE INTERFACES
61
[46] Khwaldia K, Arab-Tehrany E, Desobry S. Biopolymer coatings on paper packaging materials. Compr Rev Food Sci F. 2010;9:82–91.
[47] Eichhorn SJ, Rahatekar SS, Vignolini S, et al. New horizons for cellulose nanotechnology.
Phil Trans R Soc A. 2018;376:20170200.
[48] Memon A, Ithisoponakul S, Pramoonmak S, et al. A development of laminating mulberry
paper by biodegradable films. Energy Procedia. 2011;9:598–604.
[49] Lamberti M, Escher F. Aluminium foil as a food packaging material in comparison with
other materials. Food Rev Int. 2007;23:407–433.
[50] Bolzon G, Cornaggia G, Shahmardani M, et al. Aluminum laminates in beverage packaging: models and experiences. Beverages. 2015;1:183–193.
[51] The future of metal packaging and coatings to 2023. https://www.smitherspira.com/../
packaging/metal-packaging-and-coatings-to-2021 (Accessed 2018 April 17).
[52] Rezaul M, Shishir I, Taip S, et al. Effect of packaging materials and storage temperature on
the retention of physicochemical properties of vacuum packed pink guava powder. Food
Pack Shelf Life. 2017;12:83–90.
[53] Caiazzo F, Brambilla L, Montanari A, et al. Analysis and morphological characterization of
commercial tinplate for food packaging. Chem Surf Interface. 2018;50:430–440.
[54] Che Y, Han Z, Luo B, et al. Corrosion mechanism differences of tinplate in aerated and
deaerated citric acid solution Int. J Electrochem Sci. 2012;7:9997–10007.
[55] Wang K, Wang J, Wang HF, et al. Corrosion detection of tinplate cans containing coffee
using EIS/EN sensor. Cent South Univ. 2014;21:76.
[56] Global tinplate market (value, volume) 2018–2023-focus on packaging, electronics, construction and others. [cited 17 April 2019]. Available from: ResearchAndMarkets.
comhttps://www.researchandmarkets.com/research/2czr4l/global_tinplate?w=4
[57] Biji KB, Shamseer RM, Mohan CO, et al. Effect of thermal processing on the biochemical
constituents of green mussel (Perna viridis) in Tin-free-steel cans. J Food Sci Technol.
2015;52:6804.
[58] Ganjeh M, Mahdi S, Morad J, et al. Modeling corrosion trends in tin-free steel and tinplate
cans containing tomato paste via adaptive-network-based fuzzy inference system. J Food
Process Eng. 2017;40:e12580.
[59] Poyatos-Racionero E, Vicente Ros-Lis J, Vivancos J, et al. Recent advances on intelligent
packaging as tools to reduce food waste. J Clean Prod. 2018;172:3398–3409.
[60] Pavelkov A. Time temperature indicators as devices intelligent packaging. Acta Univ Agric
Silvic Mendel Brun LXI. 2012; 2; 245–251.
[61] Pereira V, Arruda I, Stefani R. Active chitosan/PVA films with anthocyanins from Brassica
oleraceae (Red Cabbage) as Time–temperature Indicators for application in intelligent
food packaging. Food Hydrocoll. 2015;43:180–188.
[62] Janjarasskul T, Suppakul P. Active and intelligent packaging: the indication of quality and
safety. Crit Rev Food Sci Nutr. 2018;58:808–831.
[63] Majid I, Thakur M, Nanda V. Innovative and safe packaging technologies for food and
beverages: updated Review. In: Panda S, Shetty P, editors. Innovations in technologies for
fermented food and beverage industries. Food microbiology and food safety. Cham:
Springer; 2018. p. 257–287.
[64] Frankær C, Hussain K, Rosenberg M, et al. Biocompatible microporous organically
modified silicate material with rapid internal diffusion of protons. ACS Sens.
2018;3:692–699.
[65] Krepker M, Prinz-Setter O, Shemesh R, et al. Alperstein D and Segal E. Antimicrobial
carvacrol-containing polypropylene films: composition, structure and function. Polymers.
2018;10:79.
[66] Dehghani S, ValiHosseini S, Regenstein J. Edible films and coatings in seafood preservation: a review. Food Chem. 2018;240:505–513.
[67] Dudnyk I, Janeček E, Vaucher-Joset J, et al. Edible sensors for meat and seafood freshness.
Sensor Actuat B-Chem. 2018;259:1108–1112.
62
C. I. IDUMAH ET AL.
[68] Noori S, Zeynali F, Almasi H. Antimicrobial and antioxidant efficiency of nanoemulsionbased edible coating containing ginger (Zingiber officinale) essential oil and its effect on
safety and quality attributes of chicken breast fillets. Food Control. 2018;84:312–320.
[69] Wang F, Hu Q, Mariga A, et al. Effect of nano packaging on preservation quality of
Nanjing 9108 rice variety at high temperature and humidity. Food Chem. 2018;239:23–31.
[70] Shen Z, Chen G, Chen L, et al. Utilization of smart nanomaterials for fruit fresh keeping.
In: Zhao P, Ouyang Y, Xu M, et al, editors. Applied sciences in graphic communication
and packaging. Lecture notes in electrical engineering. Singapore: Springer; 2018. p. 477.
[71] Hong J, Xu Z, Chen J, et al. High-efficiency revolving-turret chip transferring technology
for flip chip packaging. IEEE Trans Compon Packaging Manuf Technol. 2018;8:154–164.
[72] Singh S, Gaikwad K, Lee M, et al. Microwave-assisted micro-encapsulation of phase
change material using zein for smart food packaging applications. J Therm Anal
Calorim. 2018;131:2187–2195.
[73] Mehyar GF, Holley RA. Active packaging and nonthermal processing. In: Pascall MA, Han
JH, editors. Packaging for nonthermal processing of food. USA: Wiley-Blackwell; 2018. p.
1. DOI:10.1002/9781119126881.ch2.
[74] Mallardo S, De Vito V, Malinconico M, et al. Biodegradable poly (butylene succinate)based composites for food packaging. In: Cocca M, Di Pace E, Errico M, et al (eds)
Proceedings of the international conference on microplastic pollution in the mediterranean sea, 2018. Springer Water. Springer, Cham.
[75] Gaikwad K, Singh S, Lee Y. Oxygen scavenging films in food packaging. Environ Chem
Lett. 2018;1:16.
[76] Kenyó C, Renner K, Móczó J, et al. Hips/zeolite hybrid composites as active packaging
materials: structure and functional properties. Eur Polym J. 2018;103:88–94.
[77] Kumar S, Monika S, Neeraj N, et al. Recent advances and remaining challenges for
polymeric nanocomposites in healthcare applications. Prog Polym Sci. 2018;80:1–38.
[78] Mohammadi H, Kamkar A, Misaghi A. Nanocomposite films based on CMC, okra
mucilage and ZnO nanoparticles: physico mechanical and antibacterial properties.
Carbohydr Polym. 2018;181:351–357.
[79] Moura M, Mattoso L, Zucolotto V. Development of cellulose-based bactericidal nanocomposites containing silver nanoparticles and their use as active food packaging. J Food Eng.
2012;109:520–552.
[80] Tian X, Jiang X, Welch C, et al. Bactericidal effects of silver nanoparticles on lactobacilli
and the underlying mechanism. ACS Appl Mater Interfaces. 2018;10:8443–8450.
[81] Reguera C, Sanllorente S, Herrero A, et al. Study of the effect of the presence of silver
nanoparticles on migration of bisphenol A from polycarbonate glasses into food simulants.
Chemom Intell Lab Syst. 2018;176:66–73.
[82] Zapata P, Tamayo L, Páez M, et al. Nanocomposites based on polyethylene and nanosilver
particles produced by metallocenic “in situ” polymerization: synthesis, characterization,
and antimicrobial behavior. Eur Polym J. 2011;47(8):1541–1549.
[83] Castro-Mayorga L, Freitas F, Reis M, et al. Biosynthesis of silver nanoparticles and
polyhydroxybutyrate nanocomposites of interest in antimicrobial applications. Int J Biol
Macromol. 2018;108:426–435.
[84] Dey R, Bhunia R, Hussain S, et al. Flexible and free-standing films containing cobalt-doped
nanocrystalline zinc oxide dispersed in polyvinylidene fluoride matrix: synthesis and
characterization. Polym Bull. 2018;75:307–325.
[85] Zhang L, Chen J, Yu W, et al. Antimicrobial nanocomposites prepared from montmorillonite/Ag+/quaternary ammonium nitrate. J nanometer. 2018;1:1–7.
[86] Goudarzi V, Shahabi-Ghahfarrokhi I. Photo-producible and photo-degradable starch/TiO2
bionanocomposite as a food packaging material: development and characterization. Int J
Biol Macromol. 2018;106:661–669.
[87] Milovanovic S, Hollermann G, Errenst C, et al. Supercritical CO2 impregnation of PLA/
PCL films with natural substances for bacterial growth control in food packaging. Food
Res Int. 2018;107:486–495.
COMPOSITE INTERFACES
63
[88] Zhu Z, Cai H, Sun D. Titanium dioxide (TiO2) photocatalysis technology for nonthermal
inactivation of microorganisms in foods. Trends Food Sci Technol. 2018;75:23–35.
[89] Dhanasekar M, Jenefer V, Nambiar R, et al. Ambient light antimicrobial activity of
reduced graphene oxide supported metal doped TiO2 nanoparticles and their PVA based
polymer nanocomposite films. Mater Res Bull. 2018;97:238–243.
[90] Wanag A, Rokicka P, Kusiak-Nejman E, et al. Antibacterial properties of TiO2 modified
with reduced graphene oxide. Ecotoxicol Environ Saf. 2018;147:788–793.
[91] Farahnaky A, Sharifi S, Imani B, et al. Physicochemical and mechanical properties of
pectin-carbon nanotubes films produced by chemical bonding. Food Pack Shelf Life.
2018;16:8–14.
[92] Cammisuli F, Giordani S, Gianoncelli A, et al. Iron-related toxicity of singlewalled carbon
nanotubes and crocidolite fibres in human mesothelial cells investigated by ynchrotron
XRD microscopy. Sci Rep. 2018;15(8):706.
[93] Álvarez-Hernández MH, Artés-Hernández F, Ávalos-Belmontes F, et al. Current scenario
of adsorbent materials used in ethylene scavenging systems to extend fruit and vegetable
postharvest life. Food Bioprocess Technol. 2018;11:511.
[94] Huang Y, Zeng X, Zhu Q, et al. Development of an active packaging with molecularly
imprinted polymers for beef preservation. Packag Technol Sci. 2018;31:213–220.
[95] Wilson CT, Harte J, Almenar E. Effects of sachet presence on consumer product perception and active packaging acceptability - A study of fresh-cut cantaloupe. LWT.
2018;92:531–539.
[96] Lee J, Chang Y, Song H, et al. Ascorbic acid-based oxygen scavenger in active food
packaging system for raw meatloaf. Food Eng Mat Sci Nanotechnol. 2018;3:83.
[97] Yang D, Li D, Xu W, et al. Design and application of a passive modified atmosphere
packaging for maintaining the freshness of Chinese cabbage. LWT. 2018;94:136–141.
[98] Yang X, Wu S, Hopkins D, et al. Proteomic analysis to investigate color changes of chilled
beef longissimus steaks held under carbon monoxide and high oxygen packaging. Meat
Sci. 2018;142:23–31.
[99] Galstyan V, Bhandari MP, Sberveglieri V, et al. Metal oxide nanostructures in food
applications: quality control and packaging. Chemosensors. 2018;6:16.
[100] Gorrasi G, Bugatti V, Sorrentino A. Nanohybrid active fillers in food contact bio-based
materials. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications.
Cham: Springer; 2018. p. 71–87.
[101] Rizzo P, Cozzolino A, Albunia A, et al. Packaging technology for improving shelf-life of
fruits based on a nanoporous–crystalline polymer. J Appl Polym Sci. 2018;135:46256.
[102] Ciannamea E, Castillo LC, Barbosa S, et al. Barrier properties and mechanical strength of
bio-renewable, heat-sealable films based on gelatin, glycerol and soybean oil for sustainable
food packaging. React Funct Polym. 2018;125:29–36.
[103] Khaswar S, Endang W, Sri Y, et al. Nano zeolite-KMnO4 as ethylene adsorber in active
packaging of horticulture products (Musa Paradisiaca). IJSBAR. 2018;30:93–103.
[104] Djenane D, Roncalés P. Carbon monoxide in meat and fish packaging: advantages and
limits. Foods. 2018;7:12.
[105] Sängerlaub S, Miesbauer O, Michael L, et al. Humidity regulation by stretched PP and PLA
films with dispersed CaCl2. J Appl Polym Sci. 2018;135:45713.
[106] Boz Z, Welt BA, Brecht JK, et al. Review of challenges and advances in modification of
food package headspace gases. Japr. 2018;10:5.
[107] Falagán N, Leon A. Recent advances in controlled and modified atmosphere of fresh
produce. Terry Johnson Matthey Technol Rev. 2018;62:107.
[108] Liu S, Li X, Chen L, et al. Tunable d-limonene permeability in starch-based nanocomposite
films reinforced by cellulose nanocrystals. J Agric Food Chem. 2018;66:979–987.
[109] Swaroop C, Shukla M. Nano-magnesium oxide reinforced polylactic acid biofilms for food
packaging applications. Int J Biol Macromol. 2018;113:729–736.
64
C. I. IDUMAH ET AL.
[110] Siripatrawan U. Hyperspectral imaging for rapid evaluation and visualization of quality
deterioration index of vacuum packaged dry-cured sausages. Sens Actuators B Chem.
2018;254:1025–1032.
[111] Ozogul Y, Durmus M, Boga E, et al. The function of emulsions on the biogenic amine
formation and their indices of sea bass fillets (Dicentrarchus Labrax) stored in vacuum
packaging. J Food Sci. 2018;8:318–325.
[112] Bakhtiary F, Sayevand H, Mousavi A, et al. Antibacterial efficacy of essential oils and
sodium nitrite in vacuum processed beef fillet. Appl Food Biotechnol. 2018;5:1–10.
[113] Bumbudsanpharoke N, Ko S. The green fabrication, characterization and evaluation of
catalytic antioxidation of gold nanoparticle-lignocellulose composite papers for active
packaging. Int J Biol Macromol. 2018;107(Part B):1782–1791.
[114] Bosco AD, Mattioli S, Cullere M, et al. Effect of diet and packaging system on the oxidative
status and polyunsaturated fatty acid content of rabbit meat during retail display. Meat Sci.
2018;143:46–51.
[115] Liu L, Shen Z, Liang L, et al. Graphene for reducing bubble defects and enhancing
mechanical properties of graphene/cellulose acetate composite films. J Mater Sci.
2014;49:321–328.
[116] Seoane IT, Manfredi LB, Cyras VP. Bilayer biocomposites based on coated cellulose
paperboard with films of polyhydroxybutyrate/cellulose nanocrystals. Cellulose.
2018;25:2419–2434.
[117] Olesen S, Giacalone D. The influence of packaging on consumers’ quality perception of
carrots. J Sens Stud. 2018;33:e12310.
[118] Cao Y, Chen T, Wang W, et al. Construction and functional assessment of zein thin film
incorporating spindle-like ZnO crystals. RSC Adv. 2017;7:2180.
[119] Kaiser K, Schmid M, Schlummer M. Recycling of Polymer-based multilayer packaging: a
Review. Recycling. 2018;3:1.
[120] Xie J, Wang Z, Zhao Q, et al. Scale-Up fabrication of biodegradable Poly (butylene adipateco-terephthalate)/organophilic–clay nanocomposite films for potential packaging applications. ACS Omega. 2018;3(1):1187–1196.
[121] Barik S, Badamali SK. Layer double hydroxide reinforced polymer bionanocomposites for
packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging
applications. Cham: Springer; 2018. p. 269–289.
[122] Majeed Z, Ramli N, Mansor N, et al. A comprehensive review on biodegradable polymers and
their blends used in controlled release fertilizer processes. Rev Chem Eng. 2015;31:69–95.
[123] Majeed K, Arjmandi R, Hassan A. LDPE/RH/MAPE/MMT nanocomposite films for
packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging
applications. Cham: Springer; 2018. p. 209–223.
[124] Swain SK, Sarkar N, Patra B, et al. Polymer-based bionanocomposites for future packaging
materials. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications.
Cham: Springer; 2018. p. 107–121.
[125] Carrión-Granda X, Fernández-Pan I, Rovira J, et al. Effect of antimicrobial edible coatings
and modified atmosphere packaging on the microbiological quality of cold stored hake
(Merluccius merluccius) fillets. J Food Qual. 2018;2018: 1–12. Article ID 6194906.
[126] Abel N, Rotabakk B, Rustad T, et al. The influence of lipid composition, storage temperature, and modified atmospheric gas combinations on the solubility of CO2 in a seafood
model product. J Food Eng. 2018;216:151–158.
[127] Riudavets J, Pons M, Messeguer J, et al. Effect of CO2 modified atmosphere packaging on
aflatoxin production in maize infested with Sitophilus zeamais. J Stored Prod Res.
2018;77:89–91.
[128] Simko I, Hayes RJ, Truco M, et al. Molecular markers reliably predict postharvest
deterioration of fresh-cut lettuce in modified atmosphere packaging. Hort J. 2018;5:21.
[129] Vermeulen A, Devlieghere F, Ragaert P. Optimal packaging design and innovative packaging technologies for minimally processed fresh produce. In: Pérez-Rodríguez F,
Skandamis P, Valdramidis V, editors. Quantitative methods for food safety and quality
COMPOSITE INTERFACES
[130]
[131]
[132]
[133]
[134]
[135]
[136]
[137]
[138]
[139]
[140]
[141]
[142]
[143]
[144]
[145]
[146]
65
in the vegetable industry. Food microbiology and food safety. Cham: Springer; 2018. p.
193–212.
Klein D, Herbert U, Kreyenschmidt J, et al. Detection of volatile organic compounds
arising from chicken breast filets under modified atmosphere packaging using TD-GC/MS.
Food Anal Methods. 2018;11:88–98.
Paulsen E, Barrios S, Baenas N, et al. Effect of temperature on glucosinolate content and
shelf life of ready-to-eat broccoli florets packaged in passive modified atmosphere.
Postharvest Biol Tec. 2018;138:125–133.
Hilgarth M, Fuertes-Pèrez S, Ehrmann M, et al. An adapted isolation procedure reveals
Photobacterium spp. as common spoilers on modified atmosphere packaged meats. Lett
Appl Microbiol. 2018;66:262–267.
Cozzolino R, Cefola M, Pace B, et al. Quality, sensory and volatile profiles of fresh-cut big
top nectarines cold stored in air or modified atmosphere packaging. Int J Food Sci
Technol. 2018;53(7):1736–1743.
Ro E, Kim G, Kwon D, et al. Effects of natural antimicrobials with modified atmosphere
packaging on the growth kinetics of Listeria monocytogenes in ravioli at various temperatures. J Food Saf. 2018;38:e12392.
Lahmar A, Morcuende D, Andrade M, et al. Prolonging shelf life of lamb cutlets packed
under high-oxygen modified atmosphere by spraying essential oils from North-African
plants. Meat Sci. 2018;139:56–64.
Matar C, Gaucel S, Gontard N, et al. Predicting shelf life gain of fresh strawberries
‘Charlotte cv’ in modified atmosphere packaging. Postharvest Biol Tec. 2018;142:28–38.
Candir E, Ozdemir A, Aksoy M. Effects of chitosan coating and modified atmosphere
packaging on postharvest quality and bioactive compounds of pomegranate fruit cv.
‘Hicaznar’ Scientia Horticulturae. 2018;235:235–243.
Villalobos MC, Serradilla MJ, Martín A, et al. Influence of modified atmosphere
packaging (MAP) on aroma quality of figs (Ficus carica L.). Postharvest Biol Tec.
2018;136:145–151.
Pinela J, Barros L, Barreira J, et al. Postharvest changes in the phenolic profile of watercress
induced by post-packaging irradiation and modified atmosphere packaging. Food Chem.
2018;254:70–77.
Joshi K, Warby J, Valverde J, et al. Impact of cold chain and product variability on quality
attributes of modified atmosphere packed mushrooms (Agaricus bisporus) throughout
distribution. J Food Eng. 2018;232:44–55.
Liamnimitr N, Thammawong M, Techavuthiporn C, et al. Optimization of bulk modified
atmosphere packaging for long-term storage of ‘Fuyu’ persimmon fruit. Postharvest Biol
Tec. 2018;135:1–7.
Ioannidis A-G, Walgraeve C, Vanderroost M, et al. Non-destructive measurement of
volatile organic compounds in modified atmosphere packaged poultry using SPMESIFT-MS in tandem with Headspace TD-GC-MS. Food Analytical Methods.
2017;11:848–861.
Zhai Y, Huang J, Khan I, et al. Shelf-Life of boiled salted duck meat stored under normal
and modified atmosphere. Int J Food Microbiol. 2018;83:147–152.
Mudau AR, Soundy P, Araya HT, et al. Influence of modified atmosphere packaging on
postharvest quality of baby spinach (Spinacia oleracea L.) Leaves. HortScience.
2018;53:224–230.
Xu Y, Rehmani N, Alsubaie L, et al. Tapioca starch active nanocomposite films and their
antimicrobial effectiveness on ready-to-eat chicken meat. Food Packaging Shelf.
2018;16:86–91.
Saliu F, Pergola R. Carbon dioxide colorimetric indicators for food packaging application:
applicability of anthocyanin and poly-lysine mixtures. Sensor Actuat B-Chem.
2018;258:1117–1124.
66
C. I. IDUMAH ET AL.
[147] Maleki G, Sedaghat N, Woltering E, et al. Chitosan-limonene coating in combination with
modified atmosphere packaging preserve postharvest quality of cucumber during storage.
Food Measure. 2018. DOI:10.1007/s11694-018-9776-6
[148] Wang Z, Zhao S, Kang H, et al. Mussel byssus-inspired engineering of synergistic
nanointerfacial interactions as sacrificial bonds into carbon nanotube-reinforced soy
protein/nanofibrillated cellulose nanocomposites: versatile mechanical enhancement.
Appl Surf Sci. 2018;434:1086–1100.
[149] Wang Q, Lei J, Ma J, et al. Effect of chitosan-carvacrol coating on the quality of pacific
white shrimp during iced storage as affected by caprylic acid. Int J Biol Macromol.
2018;106:123–129.
[150] Wang H, Chen M, Jin C, et al. Antibacterial [2-(Methacryloyloxy) ethyl] trimethylammonium chloride functionalized reduced graphene oxide/poly(ethylene-co-vinyl alcohol)
multilayer barrier film for food packaging. J Agric Food Chem. 2018;66:732–739.
[151] Patiño L, Castellanos D, Herrera A. Influence of 1-MCP and modified atmosphere packaging in the quality and preservation of fresh basil. Postharvest Biol Tec. 2018;136:57–65.
[152] Mangaraj S, Goswami TK, Pramod M. Applications of plastic films for modified atmosphere packaging of fruits and vegetables: a Review. Food Eng Rev. 2018;1:133–158.
[153] Tornuk F, Sagdic O, Hancer M, et al. Development of LLDPE based active nanocomposite films with nanoclays impregnated with volatile compounds. Food Res Int.
2018;107:337–345.
[154] Romero-Bastida CA, Chávez M, Luis G,A, et al. Rheological properties of nanocompositeforming solutions and film based on montmorillonite and corn starch with different
amylose content. Carbohyd Polym. 2018;188:121–127.
[155] Perumal A, Sellamuthu P, Nambiar R, et al. Effects of multiscale rice straw (Oryza sativa)
as reinforcing filler in montmorillonite-polyvinyl alcohol biocomposite packaging film for
enhancing the storability of postharvest mango fruit (Mangifera indica L.). Appl Clay Sci.
2018;158:1–10.
[156] Jagadish K, Shiralgi Y, Chandrashekar B, et al. Ecofriendly synthesis of metal/metal oxide
nanoparticles and their application in food packaging and food preservation. Vol. 12. In:
Grumezescu AM, Holban AM, editors. Impact of nanoscience in the food industry.
London, UK: Elsevier; 2018. p. 197–216.
[157] Khalil H, Tye Y, Leh C, et al. Cellulose reinforced biodegradable polymer composite film
for packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 49–69.
[158] Kale R, Gorade V. Preparation of acylated microcrystalline cellulose using olive oil and its
reinforcing effect on poly (lactic acid) films for packaging application. J Polym Res.
2018;25:81. Available from: “https://link.springer.com/journal/10965“\o”Journal of
Polymer Research”
[159] Faradilla RH, Lee G, Roberts J, et al. Effect of glycerol, nanoclay and graphene oxide on
physicochemical properties of biodegradable nanocellulose plastic sourced from banana
pseudo-stem. Cellulose. 2018;25:399–416.
[160] Pradipasena P, Chollakup R, Tantratian S. Formation and characterization of BC and BCpaper pulp films for packaging application. J Thermoplast Compos Mater. 2018;31:500–
513.
[161] Cherpinski A, Torres-Giner S, Cabedo L, et al. Multilayer structures based on annealed
electrospun biopolymer coatings of interest in water and aroma barrier fiber-based food
packaging applications. J Appl Polym Sci. 2018;135:45501.
[162] Sarwar M, Niazi M, Zaib J, et al. Preparation and characterization of PVA/nanocellulose/
Ag nanocomposite films for antimicrobial food packaging. Carbohyd Polym.
2018;184:453–464.
[163] Quero F, Padilla C, Campos V, et al. Stress transfer and matrix-cohesive fracture mechanism in microfibrillated cellulose-gelatin nanocomposite films. Carbohyd Polym.
2018;195:89–98.
COMPOSITE INTERFACES
67
[164] Jin S, Li K, Li J. Nature-inspired green procedure for improving performance of proteinbased nanocomposites via introduction of nanofibrillated cellulose-stablized graphene/
carbon nanotubes hybrid. Polymers. 2018;10:270.
[165] Sun Q, Zhao X, Wang D, et al. Preparation and characterization of nanocrystalline cellulose/
Eucommia ulmoides gum nanocomposite film. Carbohyd Polym. 2018;181:825–832.
[166] Sun L, Wang W, Zeng W, et al. Soy protein-based films incorporated with cellulose
nanocrystals and pine needle extract for active packaging. Ind Crop Prod. 2018;112:412–419.
[167] Lotfi M, Tajik H, Moradi M, et al. Nanostructured chitosan/monolaurin film: preparation,
characterization and antimicrobial activity against Listeria monocytogenes on ultrafiltered
white cheese. LWT. 2018;92:576–583.
[168] Luo F, Guo K, Zhao Q, et al. Effect of cellulose whisker and ammonium polyphosphate on
thermal properties and flammability performance of rigid polyurethane foam. J Therm
Anal Calorim. 2015;122:717.
[169] Xie A, Wang Y, Jiang P, et al. Nondestructive functionalization of carbon nanotubes by
combining mussel-inspired chemistry and RAFT polymerization: towards high dielectric
nanocomposites with improved thermal management capability. Compos Sci Technol.
2018;154:154–164.
[170] Jabeen S, Kausar A, Muhammad B, et al. A Review on polymeric nanocomposites of
nanodiamond, carbon nanotube, and nanobifiller: structure, preparation and properties.
Polym Plast Technol Eng. 2015;54:1379–1409.
[171] Maity D, Rajavel K, Kumar R. Polyvinyl alcohol wrapped multiwall carbon nanotube
(MWCNTs) network on fabrics for wearable room temperature ethanol sensor. Sensor
Actuat B-Chem. 2018;261:297–306.
[172] Samsudin H, Auras R, Burgess G, et al. Migration of antioxidants from polylactic acid
films, a parameter estimation approach: part I – A model including convective mass
transfer coefficient. Food Res Int. 2018;105:920–929.
[173] Montes S, Etxeberria A, Mocholi V, et al. Effect of combining cellulose nanocrystals and
graphene nanoplatelets on the properties of poly (lactic acid) based films. Express Polym
Lett. 2018;12:543–555.
[174] Quiñones-Jurado ZV, Waldo-Mendoza MA, Mata-Padilla J, et al. Transparent low electrostatic charge films based on carbon nanotubes and polypropylene. Homopolymer Cast
Films. Polymers. 2018;10:55.
[175] Fernandez-Bats I, Pierro P, Villalonga-Santana R, et al. Bioactive mesoporous silica
nanocomposite films obtained from native and transglutaminase-crosslinked bitter vetch
proteins. Food Hydrocoll. 2018;82:106–115.
[176] Lai J, Rahman M, Hamdan S. Comparative studies of thermo-mechanical and morphological properties of polylactic acid/fumed silica/clay (1.28E) and polylactic acid/fumed
silica/clay (1.34TCN) nanocomposites. Polym Bull. 2018;75:135.
[177] Tabatabaei R, Jafari S, Mirzaei H, et al. Preparation and characterization of nano-SiO2
reinforced gelatin-k-carrageenan biocomposites. Int J Biol Macromol. 2018;111:1091–
1099.
[178] Abdelghany AM, Morsi MA, Abdelrazek A, et al. Role of silica nanoparticles on structural,
optical and morphological properties of poly (vinyl chloride-co-vinyl acetate-co-2- hydroxypropyl acrylate) copolymer. Silicon. 2018;10:519.
[179] Garcia M, Vliet G, Jain S, et al. Polypropylene/SiO2 nanocomposites with improved
mechanical properties. RevAdv Mater Sci. 2004;6:169–175.
[180] Hadi NJ, Mohamed DJ. Study the relation between flow, thermal and mechanical properties of waste polypropylene filled silica nanoparticles. Key Eng Mater. 2016;724:28–38.
[181] Painuli R, Raghav S, Kumar D. Synthesis and application of silica nanoparticles-based
biohybrid sorbents. In: Bhardwaj Mishra S, Mishra A, editors. Bio- and nanosorbents
from natural resources. springer series on polymer and composite materials. Cham:
Springer; 2018. p. 161–182.
68
C. I. IDUMAH ET AL.
[182] Lima RA, Oliveira RR, Wataya CH, et al. Biodegradable starch/copolyesters film reinforced
with silica nanoparticles: preparation and characterization. In: Carpenter JS, editor.
Characterization of minerals, metals, and materials. Cham: Springer; 2015. p. 687–693.
[183] Salama A, Diab M, Abou-Zeid R, et al. Crosslinked alginate/silica/zinc oxide nanocomposite: a sustainable material with antibacterial properties. Compos Commun. 2018;7:7–11.
[184] Kisku S, Sarkar N, Dash S, et al. Preparation of starch/PVA/CaCO3 nanobiocomposite
films: study of fire retardant, thermal resistant, gas barrier and biodegradable properties.
Polym-Plast Technol Eng. 2018;53:16.
[185] Wu Z, Wu J, Peng T, et al. Preparation and Application of Starch/Polyvinyl alcohol/citric
acid ternary blend antimicrobial functional food packaging films. Polymers. 2017;9:102.
[186] Turan D, Gunes G, Kilic A. Perspectives of bio-nanocomposites for food packaging
applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging applications. Cham: Springer; 2018. p. 1–32.
[187] Chatterjee S, Karam T, Rosu C, et al. Silica–conjugated polymer hybrid fluorescent
nanoparticles: preparation by surface-initiated polymerization and spectroscopic studies.
J Phys Chem C. 2018;122:6963–6975.
[188] Mallegni N, Phuong T, Coltelli M, et al. Poly (lactic acid) (PLA) based tear resistant and
biodegradable flexible films by blown film extrusion. Materials. 2018;11:148.
[189] Kasaai MR. Nanosized particles of silica and its derivatives for applications in various
branches of food and nutrition sectors. J nanotechnol 2015. Article ID 852394.
[190] Hoseinnejad M. Jafari S and Katouzian I. Inorganic and metal nanoparticles and their
antimicrobial activity in food packaging applications. Crit Rev Microbiol. 2018;44:2018.
[191] Sahin M, Krawczyk K, Roszkowski P, et al. Photoactive silica nanoparticles: influence of
surface functionalization on migration and kinetics of radical-induced photopolymerization reactions. Eur Polym J. 2018;98:430–438.
[192] Ros-Lis JV, Bernardos A, É P, et al. Functionalized silica nanomaterials as a new tool for
new industrial applications. In: Grumezescu AM, Holban AM, editors. Impact of
nanoscience in the food industry. A volume in handbook of food bioengineering.
London, UK: Elsevier Academic Press; 2018. p. 165–196.
[193] Neto B, Junior C, Silva E, et al. Biodegradable thermoplastic starch of peach palm (Bactris
gasipaes kunth) fruit: production and characterization. Int J Food Prop. 2018;20:S2429–
S2440.
[194] Maisanaba S, Guzmán-Guillén R, Puerto M, et al. In vitro toxicity evaluation of new
silane-modified clays and the migration extract from a derived polymer-clay nanocomposite intended to food packaging applications. J Hazard Mater. 2018;341:313–320.
[195] Hao Y, Chen Y, Li Q, et al. Preparation of starch nanocrystals through enzymatic
pretreatment from waxy potato starch. Carbohyd Polym. 2018;184:171–177.
[196] Li H, Jiang H, Ultrastiff HK. Thermoresponsive nanocomposite hydrogels composed of
ternary polymer–clay–silica networks. Macromols. 2018;51:529–539.
[197] Dai L, Li C, Zhang J, et al. Preparation and characterization of starch nanocrystals
combining ball milling with acid hydrolysis. Carbohyd Polym. 2018;180:122–127.
[198] Liu F, Shan B, Zhang S, et al. SnO2 inverse opal composite film with low-angle-dependent
structural color and enhanced mechanical strength. Langmuir. 2018;34:3918–3924.
[199] Metzger C, Sanahuja S, Behrends L, et al. Efficiently extracted cellulose nanocrystals and
starch nanoparticles and techno-functional properties of films made thereof. Coatings.
2018;8:142.
[200] Gray N, Hamzeh Y, Kaboorani A, et al. Influence of cellulose nanocrystal on strength and
properties of low density polyethylene and thermoplastic starch composites. Ind Crops
Prod. 2018;115:298–305.
[201] Malmir S, Montero B, Rico M, et al. Effects of poly (3-hydroxybutyrate-co-3-hydroxyvalerate) microparticles on morphological, mechanical, thermal, and barrier properties in
thermoplastic potato starch films. Carbohyd Polym. 2018;194:15357–15364.
[202] Benali S, Khelifa F, Lerari D, et al. Supramolecular Approach for Efficient Processing of
Polylactide/starch nanocomposites. ACS Omega. 2018;3:1069–1080.
COMPOSITE INTERFACES
69
[203] Basiak E, Lenart A, Debeaufort F. How glycerol and water contents affect the structural
and functional properties of starch-based edible films. Polymers. 2018;10:412.
[204] Hari N, Francis S, Nair A, et al. Synthesis, characterization and biological evaluation of
chitosan film incorporated with β-Carotene loaded starch nanocrystals. Food Packaging
Shelf. 2018;16:69–76.
[205] Luzi F, Fortunati E, Di Michele A, et al. Nanostructured starch combined with hydroxytyrosol in poly (vinyl alcohol) based ternary films as active packaging system. Carbohyd
Polym. 2018;193:239–248.
[206] Kumar S, Shukla A, Baul P, et al. Biodegradable hybrid nanocomposites of chitosan/gelatin
and silver nanoparticles for active food packaging applications. Food Packaging Shelf.
2018;16:178–184.
[207] Castro D, Tabary D, Martel N. Controlled release of carvacrol and curcumin: bio-based
food packaging by synergism action of TEMPO-oxidized cellulose nanocrystals and
cyclodextrin. Cellulose. 2018;25:1249.
[208] Sanyang ML, Ilyas RA, Sapuan SM, et al. Sugar palm starch-based composites for packaging applications. In: Jawaid M, Swain S, editors. Bionanocomposites for packaging
applications. Cham: Springer; 2018. p. 125–147.
[209] Xu C, Chen C, Wu D. Starch nanocrystal filled biodegradable poly (ε-caprolactone) composite membrane with highly improved properties. Carbohyd Polym. 2018;182:115–122.
[210] Qiao D, Li S, Yu L, et al. Effect of alkanol surface grafting on the hydrophobicity of starchbased films. Int J Biol Macromol. 2018;112:761–766.
[211] Fabra MJ, Martínez-Sanz M, Gómez-Mascaraque LG, et al. Structural and physicochemical
characterization of thermoplastic corn starch films containing microalgae. Carbohyd
Polym. 2018;186:184–191.
[212] Jaiber HR, Carmen L, Tadini C. Preparation and characterization of bio-nanocomposite
films based on cassava starch or chitosan, reinforced with montmorillonite or bamboo
nanofibers. Int J Biol Macromol. 2018;107(Part):A: 371–382.
[213] Silva N, Fakhouri F, Fialho R, et al. Starch–recycled gelatin composite films produced by
extrusion: physical and mechanical properties. J Appl Polym Sci. 2018;135:46254.
[214] Siddiqui M, Redhwi H, Achilias D, et al. Green synthesis of silver nanoparticles and study
of their antimicrobial properties. J Polym Environ. 2018;26:423–433.
[215] Jo Y, Garcia CV, Ko S, et al. Characterization and antibacterial properties of nanosilverapplied polyethylene and polypropylene composite films for food packaging applications.
Food Biosci. 2018;23:83–90.
[216] Mohanta YK, Nayak D, Biswas K, et al. Silver nanoparticles synthesized using wild
mushroom show potential antimicrobial activities against food borne pathogens.
Molecules. 2018;23:655.
[217] Nasab N, Jalili M, Farrokhpay S. Application of paraffin and silver coated titania nanoparticles in polyethylene nanocomposite food packaging films. J Appl Polym Sci.
2018;135:45913.
[218] Mercier-Bonin M, Despax B, Raynaud P, et al. Mucus and microbiota as emerging players
in gut nanotoxicology: the example of dietary silver and titanium dioxide nanoparticles.
Crit Rev Food Sci Nutr. 2018;58:6.
[219] Grigoriadou I, Pavlidou E, Paraskevopoulos K, et al. Comparative study of the photochemical stability of HDPE/Ag composites. Polym Degrad Stab. 2018;153:23–36.
[220] Christopher J, Hannon K, Cruz-Romero M, et al. Migration assessment of silver from
nanosilver spray coated low density polyethylene or polyester films into milk. Food
Packaging Shelf. 2018;15:144–150.
[221] Ambrusi RE, Pronsato ME, Garcí SG. Underpotential deposition and involved alloy
formation of cadmium on silver particles modified HOPG substrates. J Solid State
Electrochem. 2018;22:193.
[222] Grzelak A, Wojewódzka M, Meczynska-Wielgosz S, et al. Crucial role of chelatable iron in
silver nanoparticles induced DNA damage and cytotoxicity. Redox Biol. 2018;15:435–440.
70
C. I. IDUMAH ET AL.
[223] Sukhorukova IV, Sheveyko AN, Manakhov A, et al. Synergistic and long-lasting antibacterial effect of antibiotic-loaded Ti-Ca-PCON-Ag films against pathogenic bacteria and
fungi. Mater Sci Eng C. 2018;90:289–299.
[224] Chen Z, Lu J, Gao S, et al. Silver nanoparticles stimulate the proliferation of sulfate
reducing bacterium Desulfovibrio vulgaris. Water Res. 2018;129:163–171.
[225] Allafchian AR, Banifatemi SS, Jalali SAH. Synthesis and characterization of Ag/SiO2
nanoparticles embedded in TPS and TEOS sol-gel matrix with excellent antibacterial
activity. ?J Nanosci Nanotechnol. 2018;8:1.
[226] Jaiswal S, Mishra S. Antimicrobial and antibiofilm activity of curcumin-silver nanoparticles with improved stability and selective toxicity to bacteria over mammalian cells. P Med
Microbiol Immunol. 2018;207:39.
[227] Shanmuganathan R, MubarakAli D, Prabakar D, et al. An enhancement of antimicrobial
efficacy of biogenic and ceftriaxone-conjugated silver nanoparticles: green approach.
Environ Sci Pollut Res. 2018;25:10362.
[228] Kumar R, Howdle S, Münstedt H. Polyamide/silver antimicrobials: effect of filler types on
the silver ion release. J Biomed Mater Res B Appl Biomate. 2005;75:2311–2319.
[229] Saravanan M, Barik SK, MubarakAli DB, et al. Synthesis of silver nanoparticles from
Bacillus brevis (NCIM 2533) and their antibacterial activity against pathogenic bacteria.
Microb Pathog. 2018;116:221–226.
[230] Zhu Y, Gasilova N, Jović M, et al. Detection of antimicrobial resistance-associated proteins by
titanium dioxide-facilitated intact bacteria mass spectrometry. Chem Sci. 2018;9:2212–2221.
[231] Chawengkijwanich C, Hayata Y. Development of TiO2 powder-coated food packaging film
and its ability to inactivate Escherichia coli in vitro and in actual tests. Int J Food
Microbiol. 2008;123:288–292.
[232] Prakash J, Sun S, Swart HC, et al. Noble metals-TiO2 nanocomposites: from fundamental
mechanisms to photocatalysis, surface enhanced Raman scattering and antibacterial applications. Appl Mater Today. 2018;11:82–135.
[233] Nair RV, Gayathri PK, Gummaluri VS, et al. Large bandgap narrowing. Principles for the
oversight of nanotechnologies and nanomaterials. 2007 Available from: http://www.icta.
org/files/2012/04/080112_ICTA_rev1.pdf. (Assessed 2018 May 16th)
[234] Wiącek AE, Gozdecka A, Jurak M. Physicochemical characteristics of chitosan–tiO2
Biomaterial1. Stability and swelling properties. Ind Eng CheM Res. 2018;57:1859–1870.
[235] Cao C, Huang J, Li L, et al. Highly dispersed Ag/TiO2 via adsorptive self assembly for
bactericidal application. RSC Adv. 2017;7:13347.
[236] Wong L, Xia B, Wolvetang E, et al. Targeted, stimuli-responsive delivery of plasmid DNA
and RNA using a facile self-assembled supramolecular nanoparticle system.
Biomacromolecules. 2018;19:353–363.
[237] Nunes MR, Castilho MSM, Veeck APL, et al. Antioxidant and antimicrobial methylcellulose films containing Lippia alba extract and silver nanoparticles. Carbohyd Polym.
2018;192:37–43.
[238] Shankar S, Jong-Whan R, Won K. Preparation of poly (lactide)/lignin/silver nanoparticles
composite films with UV light barrier and antibacterial properties. Int J Biol Macromol.
2018;107(Part):B: 1724–1731.
[239] Liang S, Wang L. A Natural antibacterial-antioxidant film from soy protein isolate
incorporated with cortex phellodendron extract. Polymers. 2018;10:71.
[240] Fuertes G, Soto I, Vargas M, et al. Nanosensors for a monitoring system in intelligent and
active packaging. J Sens. 2016;2016 (Article ID 7980476). p. 1–8.
[241] Kuswandi B. Environmental friendly food nano-packaging. Environ Chem Lett.
2017;15:205–221.
[242] Gokoglan T, Soylemez S, Kesik M, et al. A novel approach for the fabrication of a flexible
glucose biosensor: the combination of vertically aligned CNTs and a conjugated polymer.
Food Chem. 2017;220:299–305.
COMPOSITE INTERFACES
71
[243] Lu J, Park BJ, Kumar B, et al. Polyaniline nanoparticle–carbon nanotube hybrid network vapour sensors with switchable chemo-electrical polarity. Nanotechnol.
2010;21:255501.
[244] Gutiérrez-Tauste D, Domènech X, Casañ-Pastor N, et al. Characterization of methylene
blue/TiO2 hybrid thin films prepared by the liquid phase deposition (LPD) method:
application for fabrication of light-activated colorimetric oxygen indicators. J Photochem
Photobiol. 2007;187:45–52.
[245] Aghaei Z, Emadzadeh B, Ghorani B, et al. Cellulose acetate nanofibres containing alizarin
as a halochromic sensor for the qualitative assessment of rainbow trout fish spoilage. Food
Bioprocess Technol. 2018;11:1087.
[246] Osada M, Sasaki T. Nanoarchitectonics in dielectric/ferroelectric layered perovskites: from
bulk 3D systems to 2D nanosheets. Dalton Trans. 2018;47:2841–2851.
[247] Dutta J, Sharma P. Fabrication, characterization and electrochemical modeling of CNT
based enzyme field effect acetylcholine biosensor. ?IEEE Sens J. 2018;18:8.
[248] Santos M, Duarte M, Nascimento G, et al. Use of TiO2 photocatalyst supported on
residues of polystyrene packaging and its applicability on the removal of food dyes.
Environ Technol. 2018;12:1–14.
[249] Buber E, Yuzer A, Soylemez S, et al. Construction and amperometric biosensing performance of a novel platform containing carbon nanotubes-zinc phthalocyanine and a
conducting polymer. Int J Biol Macromol 2018. 2017;96:61–69.
[250] Ullah M, Kausar A, Siddiq M, et al. Reinforcing effects of modified nanodiamonds on the
physical properties of polymer-based nanocomposites: a Review. Polym-Plast Technol
Eng. 2015;2018(54):861–879.
[251] Bülbül G, Hayat A, Andreescu S. Portable nanoparticle-based sensors for food safety
assessment. Sensors. 2015;1:30736–30758.
[252] Qayyum H. Nanocarriers immobilized proteases and their Industrial applications: an
overview. ?J Nanosci Nanotechnol. 2018;18:486–499.
[253] Hwang SH, Wang Z, Suh H, et al. Antioxidant activity and inhibitory effects of 2-hydroxy3-methylcyclopent-2-enone isolated from ribose–histidine Maillard reaction products on
aldose reductase and tyrosinase. Food Funct. 2018;9:1790–1799.
[254] Zdarta J, Meyer A, Jesionowski T, et al. A general overview of support materials for
enzyme immobilization: characteristics, properties, practical utility. Catalysts. 2018;8:92.
[255] Tully J, Yendluri R, Lvov Y. Halloysite clay nanotubes for enzyme immobilization.
Biomacromolecules. 2016;17:615–621.
[256] Sharma A, Singhal R, Kumar A, et al. Immobilization of glucose oxidase onto electrochemically prepared poly (aniline-co-fluoroaniline) films. J Appl Polym Sci. 2004;91:3999–
4006.
[257] Rudra JS, Dave K, Haynie DT. Antimicrobial polypeptide multilayer nanocoatings. J
Biomater Sci Polym Ed. 2006;17:1301–1315.
[258] Seidi J, Kamarian S. Free vibrations of non-uniform CNT/fiber/polymer nanocomposite
beams free vibrations of non-uniform CNT/fiber/polymer nanocomposite beams. Curved
Layer Struct. 2017;4:21–30.
[259] Bher A, Unalan I, Auras R, et al. Toughening of Poly (lactic acid) and thermoplastic
cassava starch reactive blends using graphene nanoplatelets. Polymers. 2018;10:95.
[260] Youssef B, Soumia A, Mounir E, et al. Preparation and properties of bionanocomposite
films reinforced with nanocellulose isolated from Moroccan alfa fibres. Autex Res J.
2015;15:164–172.
[261] Bashir A, Jabeen S, Gull N, et al. Co-concentration effect of silane with natural extract on
biodegradable polymeric films for food packaging. Int J Biol Macromol. 2018;106:351–359.
[262] Gobbi M, Orgiu E, Samorì P, et al. When 2D materials meet molecules: opportunities and
challenges of hybrid organic/inorganic van der waals. Heterostructures. 2018;30:181706103.
[263] Rotariu L, Lagarde F, Jaffrezic-Renault N, et al. Electrochemical biosensors for fast detection of food contaminants—trends and perspective. TRAC-Trends Anal Chem.
2016;79:80–87.
72
C. I. IDUMAH ET AL.
[264] Scarano S, Mariani S, Minunni M. Label free Affinity sensing: application to food analysis.
ACTA IMEKO. 2016;5:36–44.
[265] Arugula MA, Simonian AL. Biosensors for detection of genetically modified organisms in
food and feed. In: Arugula A, Alex L, editors. Genetically modified organisms in food.
Amsterdam, The Netherlands: Elsevier, 2016: 97–110. ISBN 978-0-12-802259-7.
[266] Templier V, Roux A, Roupioz Y, et al. Ligands for label-free detection of whole bacteria on
biosensors: a review. TRAC-Trends Anal Chem. 2016;79:71–79.
[267] Silva D, Magalhães S, Freire C, et al. Electrochemical biosensors for Salmonella: state of the
art and challenges in food safety assessment. Biosens Bioelectron. 2018;99:667–682.
[268] Vasilescu A, Marty J-L. Electrochemical aptasensors for the assessment of food quality and
safety. TRAC-Trends Anal Chem. 2016;79:60–70.
[269] Ren D, Chen L, Yuan Y, et al. Designing and preparation of fiber-reinforced composites
with enhanced interface adhesion. Polymers. 2018;10:1128.
[270] Zhang Q, Zhao X, Sui G, et al. Surface sizing treated MWCNTs and its effect on the
wettability, interfacial interaction and flexural Properties of MWCNT/Epoxy nanocomposites. Nanomaterials. 2018;8:680.