INTRODUCTION

Nanotechnology is an exciting and rapidly emerging technology allowing us

to manipulate and create materials and structures at the molecular level, often atom by

atom into functional structures having nanometer dimensions. This will make

products cheaper, production more efficient and more sustainable through using less

water and chemicals. Producing less waste and using less energy is a central concern

of food manufacturers, and the drive towards production efficiency is likely to

continue to boost nanotechnology funding. Nanoscale biotech and nano-bio-info will

have big impacts on the food and food-processing industries. The future belongs to

new products, new processes with the goal to customize and personalize the products.

More than 180 applications are in different developing stages and a few of them are

on the market already. The nanofood market is expected to surge from 2.6 bn. US

dollars today to 7.0 bn. US dollars in 2006 and to 20.4 bn. US dollars in 2010. More

than 200 Companies around the world are today active in research and development.

USA is the leader followed by Japan and China. By 2010 Asian with more than 50

percent of the world population will be the biggest market for Nanofood with the

leading of China.

Biobased nanocomposites are a new class of materials in food packaging

industry with improved barrier and mechanical properties as compared to those of

neat biopolymers. They are biodegradable and they are also produced from renewable

resources. So, these make them environment friendly. Unlike Edible films, they could

not have been consumed as a part of food. Biobased nanocomposites can be used to

extend the shelf-life of the fresh products such as fruits and vegetables by controlling

of respiratory exchange. Also it can improve the quality of fresh, frozen, and

processed meat, poultry, and seafood products by retarding moisture loss, reducing

lipid oxidation and discoloration, enhancing product appearance, and reducing oil

uptake by battered and breaded products during frying. Biobased nanocomposite is

interface between two important subjects in food packaging industry, namely Edible

films and nanocomposites. Therefore, this paper starts with short explanations about

Edible films and nanocomposites. Furthermore, a literature review about biobased

nanocomposites is presented. The last objective of this review is to explain a

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procedure for the replacement of biobased nanocomposites instead of Edible films in

food packaging industry.

To meet the increasing expectations of consumers, food must be safe, of

consistently good quality and sensory attributes, healthy and inexpensive and should

have a good shelf life. These considerations have led to ongoing extensive

investigation of suitable packaging materials for food products. In a recent era, a new

and an emerging class of clay filled polymers, called Polymer-Clay Nanocomposites

(PCN) has been developed. Properties such as superior mechanical strength, reduction

in weight, increased heat-resistance and flame retardancy, improved barrier properties

against oxygen, carbon dioxide, ultraviolet, moisture and volatiles, as well as

conservation of flavour in drinks and beverages are achievable with these novel

composites.

Applications of nanotechnology for food and beverage packaging

Nanocomposite sales volumes by packaging application (in tonnes),

2003-08

Main applications 2003 2008

Food Packaging    

Carbonated soft drinks 136 3810

Beer 862 1542

Meats 181 726

Package foods and condiments 45 726

Cheese 91 227

Juices 45 91

Others    

Pet Food 45 91

Electronics 45 91

Pharmaceuticals 45 23

Household appliances and

automotives

45 23

Total 1540 7350

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Today, food-packaging and monitoring are a major focus of food industry-

related nanotech R&D. Packaging that incorporates nanomaterials can be “smart,”

which means that it can respond to environmental conditions or repair itself or alert a

consumer to contamination and/or the presence of pathogens. According to industry

analysts, the current US market for “active, controlled and smart” packaging for foods

and beverages is an estimated $38 billion and will surpass $54 billion by 2008.

Chemical giant Bayer produces a transparent plastic film (called Durethan) containing

nanoparticles of clay. The nanoparticles are dispersed throughout the plastic and are

able to block oxygen, carbon dioxide and moisture from reaching fresh meats or other

foods. The nanoclay also makes the plastic lighter, stronger and more heat resistant.

Today, Nanocor, a subsidiary of Amcol International Corp., is producing

nanocomposites for use in plastic beer bottles that give the brew a six-month shelf-

life. By embedding nanocrystals in plastic, researchers have created a molecular

barrier that helps prevent the escape of oxygen. Nanocor and Southern Clay Products

are now working on a plastic beer bottle that may increase shelf-life to 18 months.

Kodak, best known for producing camera film, is using nanotech to develop

antimicrobial packaging for food products that will be commercially available in

2005.Kodak is also developing other ‘active packaging,’ which absorbs oxygen,

thereby keeping food fresh.

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World income generated by nanotechnologies (in billion Euros)

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700

1000

0

200

400

600

800

1000

1200

2001 2008 2010-2015

Scientists at Kraft, as well as at Rutgers University are working on nano-

particle films concentration and other packaging with embedded sensors that will

detect food pathogens. Called “electronic tongue” technology, the sensors can detect

substances in parts per trillion and would trigger a color change in the packaging to

alert the consumer if a food has become contaminated or if it has begun to spoil.

Researchers in the Netherlands are going one further to develop intelligent

packaging that will release a preservative if the food within begins to spoil. This

“release on command” preservative packaging is operated by means of a bio switch

developed through nanotechnology.

Developing small sensors to detect food-borne pathogens will not just

extend the reach of industrial agriculture and large scale food processing. In the view

of the US military, it’s a national security priority. With present technologies, testing

for microbial food-contamination takes two to seven days and the sensors that have

been developed to-date are too big to be transported easily. Several groups of

researchers in the US are developing biosensors that can detect pathogens quickly and

easily, reasoning that “super sensors” would play a crucial role in the event of a

terrorist attack on the food supply.

RFid tags could be used on food packaging to perform relatively

straightforward tasks, such as allowing cashiers in supermarkets to tally all of a

customer’s purchases at once or alerting consumers if products have reached their

expiration dates. RFid tags are controversial because they can transmit information

even after a product leaves the supermarket. Privacy advocates are concerned that

marketers will have even greater access to data on consumer behaviour.

Wal-Mart in the US and TESCO in the UK have already tested RFid tagging

on some products in some stores. The tagging of food packages will mean that food

can be monitored from farm to fork during processing, while in transit, in restaurants

or on supermarket shelves and eventually, even after the consumer buys it. Coupled

with nanosensors, those same packages can be monitored for pathogens, temperature

changes, leakages, etc.

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WHAT CAN HAPPEN INSIDE A PACKAGE?

Fresh foods just after harvest or slaughter are still active biological systems.

The atmosphere inside a package constantly changes as gases and moisture are

produced during metabolic processes. The type of packaging used will also influence

the atmosphere around the food because some plastics have poor barrier properties to

gases and moisture.

The metabolism of fresh food continues to use up oxygen in the headspace

of a package and increases the carbon dioxide concentration. At the same time water

is produced and the humidity in the headspace of the package builds up. This

encourages the growth of spoilage microorganisms and damages the fruit and

vegetable tissue.

Many food plants produce ethylene as part of their normal metabolic cycle.

This simple organic compound triggers ripening and aging. This explains why fruit

such as bananas and avocados ripen quickly to optimise the composition of the

headspace in a package.

The shelf life of processed foods is also influenced by the atmosphere

surrounding the food. For some processed foods, a lowering of oxygen is beneficial,

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Distribution in % of the global economic impact of nanotechnologies in 2010

Transports (nanomaterials,

nanoelectronics); 7%

Others; 1%

Nanomaterials; 34%

Electronics;30%

P harmaceuticals;18% Chemistry (nanostructured

catalyst); 10%

slowing down discolouration of cured meats and powdered milk and preventing

rancidity in nuts and other high fat foods. High carbon dioxide and low oxygen levels

can pose a problem in fresh produce leading to anaerobic metabolism and rapid

rotting of the food. However, in fresh and processed meats, cheeses and baked goods,

carbon dioxide may have a beneficial antimicrobial effect. when kept in the presence

of ripe or damaged fruits in a container and broccoli turns yellow even when kept in

the refrigerator.

Extensive trials have shown that each fresh food has its own optimal gas

composition and humidity level for maximising its shelf life. Active packaging offers

promise in this area; it is difficult with conventional packaging.

ACTIVE PACKAGING SYSTEMS

Active packaging employs a packaging material that interacts with the

internal gas environment to extend the shelf-life of a food. Such new technologies

continuously modify the gas environment (and may interact with the surface of the

food) by removing gases from or adding gases to the headspace inside a package.

The table below sets out some areas of atmosphere control in which active

packaging is being successfully used.

USES OF ACTIVE PACKAGING

Active Packaging System Application

Oxygen scavenging Most food classes

Carbon dioxide production Most food affected by moulds

Water vapour removal Dried and mould-sensitive foods

Ethylene removal Horticultural produce

Ethanol release Baked foods (where permitted)

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Recent technological innovations for control of specific gases within a

package involve the use of chemical scavengers to absorb a gas or alternatively other

chemicals which may release a specific gas as required.

CSIRO is conducting research to develop the right package for each

commodity. The technology being developed by CSIRO incorporates chemical

scavengers in packaging films to control such gases as ethylene or oxygen.

Ethylene scavenging

A chemical reagent, incorporated into the packaging film, traps the ethylene

produced by ripening fruit or vegetables. The reaction is irreversible and only small

quantities of the scavenger are required to remove ethylene at the concentrations at

which it is produced. A feature of the CSIRO system is its pink colour which can be

used as an indicator of the extent of reaction and shows when the scavenger is used

up.

It is expected that the film will be produced in Australia and used as a

valuable means of extending the export life of fruit, vegetables and flowers.

Systems developed in other countries are already commercially available.

These usually involve the inclusion in the package of a small sachet which contains an

appropriate scavenger. The sachet material itself is highly permeable to ethylene and

diffusion through the sachet is not a serious limitation. The reacting chemical for

ethylene is usually potassium permanganate which oxidises and inactivates it.

Oxygen scavenging

The presence of oxygen in food packages accelerates the spoilage of many

foods. Oxygen can cause off-flavour development, colour change, nutrient loss and

microbial attack. Several different systems are being investigated by CSIRO to

scavenge oxygen at appropriate rates for the requirements of different foods.

One of the most promising applications of oxygen scavenging systems in

food packages is to control mould growth. Most moulds require oxygen to grow and

in standard packages it is frequently mould growth which limits the shelf life of

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packaged baked goods such as cakes and crumpets and of packaged cheese.

Laboratory trials have shown that mould growth on some baked products can be

stopped for at least 30 days with active packaging and significant improvements in the

mould-free life of packaged cheese have also been obtained.

Another promising application is the use of active packaging to delay

oxidation of and therefore rancidity development in vegetable oils.

Again the use of discrete sachets containing oxygen absorbents has already

found commercial application. In this instance the scavenging material is usually

finely divided iron oxide. These sachets have been used in some countries to protect

the colour of packaged cured meats from oxygen in the headspace and to slow down

staling and mould growth on baked products, e.g. pizza crusts.

This approach of inserting a sachet into the package is effective but meets

with resistance among food packers. The active ingredients in most systems consist of

a non-toxic brown/black powder or aggregate which is visually unappealing if the

sachet is broken. A much more attractive approach would be the use of a transparent

packaging plastic as the scavenging medium.

Humidity control

Condensation or 'sweating' is a problem in many kinds of packaged fruit and

vegetables. It is of particular concern in cartons of fresh flowers for which there is an

important export trade.

Unless the relative humidity around flowers is kept at about 98 per cent,

water will be lost from the bunches. Such high humidities mean there is a very real

risk of condensation occurring during transport as the temperature of the flowers may

fluctuate by several degrees. When one part of the package becomes cooler than

another, water is likely to condense in the cooler areas.

If the water can be kept away from the produce there may be little harm.

However when the condensation wets the produce, nutrients leak into the water

encouraging rapid mould growth.

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CSIRO has developed technology to control condensation inside packages.

This allows the food to remain dry without drying out the product itself. Therefore

sensitive products such as flowers and table grapes are protected from contact with

water. This helps to reduce growth of mould.

Carbon dioxide release

High carbon dioxide levels are desirable in some food packages because

they inhibit surface growth of microorganisms. Fresh meat, poultry, fish, cheeses and

strawberries are foods which can benefit from packaging in a high carbon dioxide

atmosphere.

However with the introduction of modified atmosphere packaging there is a

need to generate varying concentrations of carbon dioxide to suit specific food

requirements. Since carbon dioxide is more permeable through plastic films than is

oxygen, carbon dioxide will need to be actively produced in some applications to

maintain the desired atmosphere in the package.

So far the problems associated with diffusion of gases, especially carbon

dioxide, through the package, have not been resolved and this remains an important

research topic

Ethanol

Ethanol (or common alcohol) is not a permitted food preservative in

Australia. However its antimicrobial activity is well known and it is used in medical

and pharmaceutical applications. Ethanol has been shown to increase the shelf life of

bread and other baked products when sprayed onto product surfaces prior to

packaging.

A novel method of generating ethanol vapour, recently developed in Japan,

is through the use of an ethanol releasing system enclosed in a small sachet which is

included in a food package. Food grade ethanol is absorbed onto a fine inert powder

which is enclosed in a sachet that is permeable to water vapour. Moisture is absorbed

from the food by the inert powder and ethanol vapour is released and permeates the

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sachet into the food package headspace. This system is approved in Japan to extend

the mould-free shelf life of various cakes.

Sulphur dioxide

Sulphur dioxide is a permitted preservative in Australia for some processed

foods. It can also be used to control mould growth in some fruits. Serious loss of table

grapes can occur unless precautions are taken against mould growth. It is necessary to

refrigerate grapes in combination with fumigation using low levels of sulphur dioxide.

Fumigation can be conducted in the fruit cool stores as well as in the cartons. Carton

fumigation consists of a combination of quick release and slow release systems which

emit small amounts of sulphur dioxide.

When the temperature of the cartoned grapes rises due to inadequate

temperature control, the slow release system fails releasing all its sulphur dioxide

quickly. This can lead to illegal residues in the grapes and unsightly bleaching of the

fruit.

CSIRO is working on developing systems which gradually release sulphur

dioxide and are less sensitive to high temperature and moisture than those presently

used. These systems have potential use for fresh grapes and processed foods permitted

to contain sulphur dioxide such as dried tree fruits and wine.

An Overview of ‘Smart Packaging’ and ‘Active Packaging’

Using Clay Nanoparticles to Improve Plastic Packaging for Food Products

Chemical giant Bayer produces a transparent plastic film (called Durethan)

containing nanoparticles of clay. The nanoparticles are dispersed throughout the

plastic and are able to block oxygen, carbon dioxide and moisture from reaching fresh

meats or other foods. The nanoclay also makes the plastic lighter, stronger and more

heat-resistant.

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How Creating a Molecular Barrier by Embedding Nanocrystals in Plastic Can

Improve Packaging

Until recently, industry’s quest to package beer in plastic bottles (for cheaper

transport) was unsuccessful because of spoilage and flavour problems. Today,

Nanocor, a subsidiary of Amcol International Corp., is producing nanocomposites for

use in plastic beer bottles that give the brew a six-month shelf-life. By embedding

nanocrystals in plastic, researchers have created a molecular barrier that helps prevent

the escape of oxygen. Nanocor and Southern Clay Products are now working on a

plastic beer bottle that may increase shelf-life to 18 months.

Using Nanotechnology Methods to Develop Antimicrobial Packaging and ‘Active

Packaging’

Kodak, best known for producing camera film, is using nanotech to develop

antimicrobial packaging for food products that will be commercially available in

2005. Kodak is also developing other ‘active packaging,’ which absorbs oxygen,

thereby keeping food fresh.

Embedded Sensors in Food Packaging and ‘Electronic Tongue’ Technology

Scientists at Kraft, as well as at Rutgers University and the University of

Connecticut, are working on nano-particle films and other packaging with embedded

sensors that will detect food pathogens. Called “electronic tongue” technology, the

sensors can detect substances in parts per trillion and would trigger a colour change in

the packaging to alert the consumer if a food has become contaminated or if it has

begun to spoil.

Using a Nanotech Bioswitch in ‘Release on Command’ Food Packaging

Researchers in the Netherlands are going one further to develop intelligent

packaging that will release a preservative if the food within begins to spoil. This

“release on command” preservative packaging is operated by means of a bioswitch

developed through nanotechnology.

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Using Food Packaging Sensors in Defence and Security Applications

Developing small sensors to detect food-borne pathogens will not just

extend the reach of industrial agriculture and large-scale food processing. In the view

of the US military, it’s a national security priority. With present technologies, testing

for microbial food-contamination takes two to seven days and the sensors that have

been developed to date are too big to be transported easily. Several groups of

researchers in the US are developing biosensors that can detect pathogens quickly and

easily, reasoning that “super sensors” would play a crucial role in the event of a

terrorist attack on the food supply. With USDA and National Science Foundation

funding, researchers at Purdue University are working to produce a hand-held sensor

capable of detecting a specific bacteria instantaneously from any sample. They’ve

created a start-up company called BioVitesse.

Food Packaging Industry with Biobased Nanocomposites

EDIBLE FILMS

Edible films are defined as a thin layer of edible material formed on food as

a coating. Additionally, Edible films can carry antioxidants and antimicrobials, while

traditional packaging materials can not compete in these aspects. Edible films are

used to extend the shelf life of food and maintain its quality by inhibiting the

migration of moisture, oxygen, carbon dioxide, aromas and lipids. Other favourable

aspects of Edible films are: completely biodegradable can be a part of a food and can

reduce the consumption of naphtha-based polymeric films. The properties of the

edible films which have been mostly evaluated are mechanical properties and

specially gas permeability properties. A major component of Edible films is the

plasticizer. The addition of a plasticizer agent to Edible films is required to overcome

film brittleness, caused by high intermolecular forces. Plasticizers reduce these forces

and increase the mobility of polymer chains, thereby improving flexibility and

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extensibility of the film. On the other hand, plasticizers generally decrease gas, water

vapour and solute permeability of the film and can decrease elasticity and cohesion.

Type of degradation reactions in food systems determines optimum gases composition

in food packaging. For example, oxygen is involved in many degradation reactions in

foods, such as fat and oil rancidity, microorganism growth, enzymatic browning and

vitamin loss. Thus, many packaging strategies seek to exclude oxygen in packaging to

protect the food product. On the other hand, the permeability of Edible film to oxygen

and carbon dioxide is essential for respiration in living tissues such as fresh fruits and

vegetables. So, moderate barrier materials are more appropriate. If an Edible film with

the appropriate permeability is chosen, a controlled respiratory exchange can be

established and thus the preservation of fresh fruits and vegetables can be prolonged.

So the main characteristics to consider in the selection of Edible film are their oxygen,

carbon dioxide and water vapour permeability. The success of Edible films for fresh

products totally depends on the control of internal gas composition. Semi-permeable

coatings can create a modified atmosphere (MA) similar to controlled atmosphere

(CA) storage, with less expense incurred. However, the atmosphere created by

coatings can change in response to environmental conditions, such as temperature and

humidity, due to combined effects on fruit respiration and coating permeability. Types

of deteriorative reactions, required gas composition and some case study have been

summarized in Table for important areas of food industry.

Edible films have been prepared by casting solutions of proteins,

carbohydrates and lipids, in different combinations and compositions. Edible films

which are made of proteins are most attractive. Firstly, they are supposed to provide

nutritional value. Secondly, protein-based films have impressive gas barrier properties

compared with those from lipids and polysaccharides. For example, oxygen

permeability of soy protein-based films (when they are not moist) was 500, 260, 540

and 670 times lower than that of low-density polyethylene, methylcellulose, starch

and pectin, respectively. On the other hand, their mechanical properties are also better

than those of polysaccharide and fat based films because proteins have a specific

structure which confers a wider range of functional properties, especially high

intermolecular binding potential. In addition, Proteins, such as casein, whey proteins

and corn zein, have also been used in Edible film formulation as a moisture barrier

since these proteins are abundant, cheap and readily available.

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BIOBASED NANOCOMPOSITE FILM

Biobased nanocomposites are composed of biopolymer, nanoclay and

usually compatibilizing agents. Major component of biobased nanocomposites is

biopolymers. Biopolymers have great commercial potential for bioplastic and Edible

films, but some of the properties such as brittleness, low heat distortion temperature;

high gas permeability and low melt viscosity for further processing restrict their use in

a wide range of applications. Modification of biopolymers with nanotechnology is an

effective way to improve their properties. Biopolymers derived from renewable

resources are broadly classified according to method of production. This gives the

following three main categories:

1. Biopolymers directly extracted/removed from natural materials (mainly

plants) such as hydrocolloids (polysaccharides and proteins). The most frequently

utilized polysaccharides were cellulose and starch (and their derivatives), chitosan,

seaweed extracts (carrageenans and alginates), exudates (arabic gum), seed (guar

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gum), xanthan and gellan gum and pectin. Proteins include collagen, gelatin, casein,

whey proteins, corn zein, wheat gluten and soy proteins.

2. Biopolymers produced by classical chemical synthesis from renewable

bioderived monomers like polylactate (PLA).

3. Biopolymers produced by microorganisms or genetically transformed

bacteria like Polyhydroxyalkanoates. Hence, biopolymers which can be used in

biobased nanocomposites formulation are numerous.

The utilization of special compatibilizing agents (modifier) between the two

basic materials (biopolymer and nanoclay) for the preparation of biobased

nanocomposite is necessary. Layered silicates are characterized by a periodic stacking

of mineral sheets with a weak interaction between the layers and a strong interaction

within the layer. The space in-between the layers is occupied by cations. By cation

exchange reactions between the clay and organic cations (such as alkyl ammonium

salts), the layered silicate can be transformed into organically modified clay. The

inter-layer distance will increase by using voluminous modifiers. If this modifier is

compatible with biopolymer as well, a homogeneously and nanoscaled distribution

(exfoliation) of the clay sheets can be effected in the polymer matrix. The pure clay

shows an interlayer distance of 1.26 nm. It has been proven by XRD analysis that

most of the layers are indeed swollen after the modification reaction. The inter-layer

distance changes to 2.34 nm, an increase of nearly 100% compared to the pure clay.

A comprehensive review of biobased nanocomposite film applications in

food packaging industry is necessary. Therefore, continuing this section, several

studies which are concentrated on biobased nanocomposites have been presented.

Use of Polymer-Clay Nanocomposites in Food Packaging

The concept of PCN was developed in the late 1980s. Toyota was the first

company to commercialise these nanocomposites and to use nanocomposite parts in

one of its popular models for several years. PCN are a class of hybrid materials made

from nanoscale particles such as layered silicates, for example montmorillonite

(MMT), with layer thickness in nanometer dimension. Several potential applications

have been identified so far in various industrial sectors, for example automobiles

(gasoline tanks, bumpers, interior and exterior panels etc.), construction (building

sections, structural panels), aerospace (flame retardant panels, high performance

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components), electronics and electrical (printed circuit boards, electric components),

food packaging (containers, wrapping films), and coatings and pigments. The present

review will be restricted to food packaging applications only, including a brief outline

of preparation, characterisation, properties, recent developments and future prospects.

PREPARATION AND CHARACTERISATION OF POLYMER CLAY

NANOCOMPOSITE

Researches on the preparation and characterisation of PCN intended for food

packaging have been published only since the late 1990s. Most of the research that

has been published so far involved the use of montmorillonite (MMT) clay as the

nanocomponent. A wide range of synthetic polymers such as polyethylene (PE),

nylon and PVC, and biopolymers such as starch, have been investigated. Varying

amounts of nanoclay (usually 1 to 5 weight %) (Lange and Wyser, 2003) were used in

most of the published studies on PCN. Silicates used in the synthesis of PCN are

layered with a layer thickness of around 1 nm. The lateral dimensions of these layers

can vary up to several micrometres; consequently the aspect ratio of these fillers (ratio

of length to thickness) is particularly high with values greater than 1000. These layers

form stacks with a gap between them called the ‘interlayer’ or the ‘gallery’. The

inorganic cations within the interlayers can be substituted by other cations such as

lithium and sodium. A schematic presentation of the atom arrangements in a unit cell

for a three-layer clay such as MMT is shown in Figure.

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Figure. Structure of a layered silicate

There are usually three possible arrangements of these layered silicate clays,

which can be obtained when they are dispersed in a polymer matrix:

i) Non-intercalated: if the polymer cannot intercalate between the silicate sheets, a

non-intercalated microcomposite is obtained. Beyond this traditional class of

polymer-filler composites, two other types of composites can be obtained.

ii) Intercalated structure: the separation of clay layers by increasing the interlayer

spacing.

iii) Exfoliated or delaminated structure: the complete separation of clay platelets into

random arrangements. This is the ideal nanocomposite arrangement but is harder to

achieve during synthesis and/or processing.

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Figure. Schematic representation of intercalated and exfoliated nanocomposite from layered silicate clay filler and polymer.

Usually, the structure of nanocomposites can be characterised by two

complementary analytical techniques, namely, X-ray diffraction (XRD) and

transmission electron microscopy (TEM). XRD is used to identify intercalated

structures by determination of the interlayer spacing. Intercalation of the polymer

chains increases the interlayer spacing and according to Bragg’s law, it should cause a

shift of the diffraction peak towards lower angle. However, if the spacing between the

layers becomes too large, those diffraction peaks will disappear in the X-ray

diffractograms, which implies complete exfoliation of the layered silicates in the

polymer matrix. In this case, TEM is used to identify the exfoliated silicate layers.

The nanocomposites are generally prepared by i) solution method, ii) in situ/

interlamellar polymerisation technique and iii) melt processing.

i) In the solution method, the organoclay is swollen in a solvent. The

polymer, separately dissolved in that solvent is added to it so that the polymer

molecules can crawl between the silicate layers of the filler. The solvent is then

evaporated to obtain intercalated/exfoliated nanocomposite forms.

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ii) The in-situ method, also known as interlamellar polymerisation, involves

swelling of the layered silicates by absorption of a liquid monomer, or a monomer

solution. The monomer migrates into the galleries of the layered silicate, so that

polymerisation can occur within the intercalated sheets. Polymerisation can be

initiated either by heat or radiation, by diffusion of a suitable initiator, or by an

organic initiator.

iii) The melt intercalation method involves incorporation of clay filler in the

molten state of the polymer to form the nanocomposite material. The last method is

widely accepted in nanocomposite research due to its solvent-free process.

FUTURE PROSPECTS

Due to the excellent barrier properties, PCN has major applications in food

packaging industries for processed meats, cheese, confectionary and cereals as it

enhances the shelf life of food materials. Active projects are under way both in

industries as well as in academic research laboratories. Alcoa CSI has already applied

multilayer PCN as barrier liner materials for enclosure applications. Honeywell has

developed commercial Nylon- 6/clay nanocomposite products, AegisTM NC resin,

for drink packaging applications (Auto applications drive commercialization of

nanocomposites, 2002). Mitsubishi Gas Chemical and Nanocor have jointly

developed Nylon-MXD6 nanocomposites for multilayered PET bottle applications.

By 2009, it is estimated that the flexible and rigid packaging industry will use 5

million pounds of nanocomposites materials in the beverage and food industry. By

2011, consumption is estimated to be 100 million pounds. Beer bottles are expected to

be the biggest consumer by 2006 with 3 million pounds of nanocomposites, until

carbonated soft drinks bottles are projected to surpass that with use of 50 million

pounds of nanocomposites by 2011.

Nanocomposites can also be designed to incorporate and deliver active

substances into biological systems, at low cost and with limited environmental

impact. For example, creating “bacteria-repellent” surface in packaging film which

changes colour in the presence of harmful microorganism or toxins. Nanocomposites

with these types of unique characteristics could be used for a wide range of minimally

processed and processed food products such as meat and fish products, dairy foods,

cereals, confectionery, boil-in-bag food, fruit juices, beer and carbonated drinks.

Polymer nanocomposites are the future for the global packaging industry. Once

production and material costs are reduced, companies will be using this technology to

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increase their product’s stability and shelf life so that higher quality products can be

delivered to their customers while saving money. It seems that the advantages that

nanocomposites offer far outweigh the costs and concerns, and with time the

technology will be further refined and processes more highly developed. Research

continues into other types of nanofillers (i.e. carbon nanotubes), allowing new

nanocomposite structures with different improved properties that will further advance

the use of nanocomposite in many diverse packaging applications. On the other hand,

the safety and regulatory aspects toward the use of nanocomposites as food packaging

materials will be another topic of concern in near future (IFST, 2006).

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CONCLUSIONPackaging has developed into an essential technology in the handling and

commercialization of foodstuffs to provide, by maintaining or even increasing, the

required levels of quality and safety. There are high hopes in food and packaging:

longer shelf life, safer packaging, better traceability of products and healthier food is

only a few of the expected improvements. This paper gathers a number of significant

results where nanotechnology was satisfactorily applied to improve packaged food

quality and safety by increasing the barrier and mechanical properties of biopolymer

based nanocomposite. Also researches on biobased nanocomposites have been

published indicating that the science of biobased nanocomposites for food packaging

industry is still in its infancy. It appears that the momentum of PCN utilisation is

building slowly in the world possibly due to the cost and variability in the quality of

some of the products as well as popular resistance to accepting new technology. The

potential of nanocomposites as food packaging materials is largely due to the

enhanced gas and moisture barrier properties, increased stiffness with lighter weight,

strength and thermal stability. Novel biodegradable biopolymer/clay nanocomposite

films are also developed as environmentally friendly material to reduce plastic waste.

They too provide improved strength and barrier properties that are desirable for food

packaging. More understanding of the clay modification, dispersion and polymer-

filler interaction are needed to fill the gaps.

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