• Functions of Packaging

• Protective Packaging

• Packaging Materials

• Chemical Migration into Food

• Regulations of Food Contact Materials in the EU

• Safety Aspects

• Modified Atmosphere Packaging (MAP)

• New Packaging Technologies

Functions of Packaging

Most food is consumed far removed in time and space from the point of its production, hence the need for the preservation processes. A necessary aid for the storage and distribution is packaging. The functions of packaging are several.

Packaging serves as a material handling tool containing the desired unit amount of food within a single container and may facilitate the assembly several such units into aggregates. For example, some fluids are packaged in bottles which may be placed in boxes, and these boxes in turn can be assembled into easily handled pallets.

The package may also serve as a processing aid. For instance, the metal can be used in heat sterilization of many food items serves not only a protective function but, by its dimensional stability, assures that when fully packed the food maintains a certain shape and location for which heat penetrations can be calculated.

The package is a convenience item for the consumer. The examples one could choose here are very numerous. A beer can, for instance, serves as the drinking utensil as well as a process, storage, and distribution container. A variety of packages aid in handling, preparation, and consumption of foods by the consumer.

The package is a marketing tool. The sales appeal and product identification aspects of packaging are particularly important to sales and marketing branches of food companies, and since these branches often have a dominant role in business decisions. The package must identify and provide useful information about the product. It contains a label providing information to customers such as the product name, brand, net weight, producer info, price, product date, country of origin, nutritional info, etc.

Packaging, when properly used, can be a cost saving device. Certain packages have obvious economic benefits, such as prevention of spills, ease of transporting, prevention of contamination, reduction of labour cost.
Protection of the product is the most important aspect of packaging. The package must protect the produce from mechanical damage and poor environmental conditions during handling and distribution.

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Protective Packaging

The deterioration of packaged foods depends largely on transfers that may occur between the internal environment inside the package, the external environment which is exposed to the hazards of storage and distribution. For example, there may be transfer of moisture from a humid atmosphere into a dried product, or transfer of an undesirable odour from the external atmosphere into a high fat product. In addition to the ability of packaging materials must also protect the product from mechanical damage, and prevent or minimize misuse by consumers

Packaging is directly related to food safety in two ways. Firstly, if the packaging material does not provide a suitable barrier around the food, micro-organisms can contaminate the food and make it unsafe. However, microbial contamination can also arise if the packaging material permits the transfer of, for example, moisture or oxygen from the atmosphere into the package. In this situation, microorganisms present in the food but presenting no risk because of the initial absence of moisture or oxygen may then able to grow and present a risk to the consumer. Secondly, the migration of potentially toxic compounds from some packaging materials to the food is a possibility in certain situations and gives rise to food safety concerns.

Packaging can be related to food quality in several ways. Texture, flavour, colour, appearance and nutritive value are the major quality attributes of foods. Packaging can affect the rate and magnitude of many of the quality changes. For example, development of oxidative rancidity can often be minimized if the package is an effective oxygen barrier; flavour compounds can be absorbed by some types of packaging material; the particle size of many food powders can increase (i.e. clump) if the package is a poor moisture barrier.

Effect of Environment on Food Stability and the Need for Protective Packaging
The package affects the quality of foods by controlling the degree to which factors connected with processing, storage, and handling can act on components of foods. The processing and storage factors amenable to control by packaging include light, oxygen concentration, moisture concentration, heat transfer, contamination, and attack by biological agents.

A) Light

Food can be adversely affected by prolonged exposure to light. Light promotes the following chemical reactions in food: oxidation of fats and oils to produce the complex of changes known as oxidative rancidity, changes in various pigments. To prevent such changes a packaging material which is opaque to light may be used or, where sight of the product is desirable, the packaging material may be coloured to exclude short length light waves.

B) Oxygen

Oxidation reactions are often the cause of undesirable changes in foods. One such reaction namely oxidative rancidity due to peroxidation of fats and oils in various foods. In addition many vitamins, pigments and some amino acids and proteins are oxygen sensitive. The shelf life of many foods may be extended by creating an atmosphere inside the package which has low oxygen content. This is achieved by maintaining a partial vacuum in the container or by displacing air with nitrogen or carbon dioxide (gas packaging). Cheese, cooked and cured meat products, dried meats, egg and coffee are examples of such foods. In these and other similar cases it is necessary that packaging material used should be a good barrier to gases and the package effectively sealed so that the composition of the in-pack atmosphere does not change significantly during the storage and distribution of the product.

C) Water

The water content of foods is dependent on the relative humidity of the immediate environment. Water relations of foods strongly affect packaging requirements. Foods with high equilibrium relative humidity will tend to lose moisture to the atmosphere and this can result in a loss in weight and deterioration in appearance and texture. Meat and cheese are typical examples of such foods. Product with low equilibrium relative humidity tends to absorb moisture, particularly in high humidity atmospheres, and this can also cause a loss in quality. Dry powders, such as cake mixes and custard powder, may cake, biscuits and snack foods may lose their crispness and dehydrated products may spoil if their water activity rises above the level which permits microbiological and/or chemical activity. On the other hand, in the case of fresh products with high respiration rates, i.e. some fruits and vegetables, it may be necessary to allow for the passage of water vapour out of the package, otherwise a high humidity will develop in the package and fogging may occur when the temperature fluctuates.

D) Mechanical Damage

Both fresh and processed foods are susceptible to mechanical damage. The cracking of egg shells, the bruising of fruit and the breaking of biscuits are examples. Such damage may result from: sudden impacts or shocks during handling and transport, vibration during transport by road, rail or air, and compression loads imposed while packages are stacked in warehouses or ships holds. Appropriate packaging can reduce the incidence and extent of mechanical injury. The selection of strong, rigid packaging material, e.g. metal, glass, wood and fibreboard can reduce damage due to compression loads. The inclusion of a cushioning material as a component in the package can protect against shocks and vibration. Examples of such cushioning materials are tissue paper, corrugated papers and boards, pulp board  and foamed plastics.

E) Attack by Biological Agents

1. Microorganisms
One function of package is to prevent microbiological contamination of the contents. In the case of pasteurised products, or foods preserved by drying, freezing, curing this role is vital.
The protection of package content from attack by microorganisms depends on mechanical integrity of the package (absence of breaks and seal imperfections) and on the resistance of the package to penetration by microorganisms. Microorganisms, including moulds, yeast and bacteria cannot penetrate the plastic films or metal sheets in the absence of pinholes.

2. Insect Infestation
In order to avoid insect infestation one must assure that the package contents are free of viable insect eggs or larvae, and that that the package cannot be penetrated from the outside by adults or larvae. In storage and distribution, external package environment (truck interiors, warehouses, railroad cars) should be insect free. Package is expected to provide a defence against insect penetration: Highly polished and slippery surfaces, free of debris and dust are desirable. Odour barrier combined with cleanliness of surface helps avoid insect attack. Well-formed seals and closures assure protection.

References
Sacharow S., Griffin R., 1980. Principles of Food Packaging, 2nd Edition, AVI Pub. Co.Westport, Connecticut.
Brennan J.G., Butters J.R, Cowell N.D., Lilley A.E, 1990. Food
Engineering Operations, Elsevier App. Sci., London, New York.

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Packaging Materials

Glass

Glass jars and bottles are made by heating a mixture of sand (73%), the main constituent being silica (99% SiO2), broken glass or 'cullet' (15-30% of total weight), soda ash (Na2CO3) and limestone (CaCO3 or CaCO3.MgCO3) to a temperature of 1350-1600ºC. Alumina (Al2O3) improves the chemical durability of the glass, and refining agents reduce the temperature and time required for melting, and also helps remove gas bubbles from the glass. Colorants include chromic oxide (green), iron, sulphur and carbon (amber), and cobalt oxide (blue). Flint (clear) glass contains decolourisers (nickel and cobalt) to mask any colour produced by trace amounts of impurities (e.g. iron).

Glass containers have the following advantages:

• they are impervious to moisture, gases, odours and micro-organisms

• they are inert and do not react with or migrate into food products

• they have filling speeds comparable with those of cans

• they are suitable for heat processing when hermetically sealed they are transparent to microwaves

• they are re-useable and recyclable

• they are resealable

• they are transparent to display the contents and can be decorated

• they can be moulded into a wide variety of shapes and colours

• they are perceived by the customer to add value to the product

• they are rigid, having good vertical strength to allow stacking without damage to the container.

The main disadvantages of glass include:

• higher weight which incurs higher transport costs than other types of packaging

• lower resistance than other materials to fracturing and thermal shock

• more variable dimensions than other containers

• potentially serious hazards from glass splinters or fragments in foods.

Textiles and wood

Textile containers have poor gas and moisture barrier properties, they are not suited to high-speed filling, have a poorer appearance than plastics and are a poor barrier to insects and micro-organisms. They are therefore only used as shipping containers or in a few niche markets as over-wraps for other packaging. Woven jute sacks, which are chemically treated to prevent rotting and to reduce their flammability, are non-slip which permits safe stacking, have a high resistance to tearing, low extensibility and good durability. They are used to transport a variety of bulk foods including grain, flour, sugar and salt, although they are steadily being replaced by polypropylene sacks or bulk containers. Wooden shipping containers have traditionally been used for a range of solid and liquid foods including fruits, vegetables, tea, wines, spirits and beers. They offer good mechanical protection, good stacking characteristics and a high vertical compression strength-to-weight ratio.

Metal

Hermetically sealed metal cans have advantages over other types of container in that they can withstand high temperature processing and low temperatures; they are impermeable to light, moisture, odors and micro-organisms to provide total protection of the contents; they are inherently tamperproof and the steel can be recycled by extraction from solid wastes. However, the high cost of metal and relatively high manufacturing costs make cans expensive. They are heavier than other materials, except glass, and therefore incur higher transport costs.

Flexible films
Flexible packaging describes any type of material that is not rigid, but the term flexible film is usually reserved for non-fibrous plastic polymers, which are less than 0.25 mm thick. The ability to shape plastics is due to long polymers formed by addition reactions (e.g. for polyethylene, the CH2_CH2 group splits at the double bond to form CH2 CH2 CH2), or by condensation reactions (e.g. PET, where water is eliminated between ethylene glycol and terephthalic acid) to form long polymer molecules. Thermoplastic materials are able to undergo repeated softening on heating and hardening again on cooling, whereas thermosetting plastics cross-link the long molecules when heated or treated with chemicals and they do not resoften.

• In general, flexible films have the following properties:
• they have relatively low cost
• they can be produced with a range of barrier properties against moisture and gases
• they are heat sealable to prevent leakage of contents, and can be laminated to paper, aluminium or other plastics
• they are suitable for high-speed filling
• they have wet and dry tensile and impact strength
• they are easy to handle and print and are convenient for the manufacturer, retailer and consumer
• they add little weight to the product and fit closely to the shape of the food, thereby wasting little space during storage and distribution.

Ranges of mechanical, optical, thermal and barrier properties are produced for each type of polymer by variation in film thickness, orientation of polymer molecules, amount and type of additives and in the type and thickness of coatings. Films may be used singly, coated with polymer or aluminium, or produced as multi-layered laminates or coextrusions. Plasticizers are added to soften the film and to make it more flexible, especially for use in cold climates.

Single films
Most polymer films are made by extrusion, in which pellets of the polymer are melted and extruded under pressure as a sheet or tube. Other methods are callandering, where the polymer is passed through heated rollers until the required thickness is achieved, and casting, in which the extruded polymer is cooled on chilled rollers.

Cellulose films are produced by mixing sulphite paper pulp with caustic soda to dissolve it and it is allowed to ripen for 2 3 days to reduce the length of polymer chains and form sodium cellulose. This is then converted to cellulose xanthate by treatment with carbon disulphide, ripened for 4 5 days to form viscose, and then cellulose is regenerated by extrusion or casting into an acid salt bath to form cellulose hydrate. Glycerol is added as a softener and the film is then dried on heated rollers.
Oriented polypropylene (OPP) is a clear glossy film with good optical properties and a high tensile strength and puncture resistance. It has moderate permeability to moisture, gases and odors, which is not affected by changes in humidity. It is thermoplastic and therefore stretches, although less than polyethylene, and has low friction, which minimizes static buildup and makes it suitable for high-speed filling equipment. Biaxially oriented polypropylene (BOPP) has similar properties to oriented polypropylene but is much stronger. PP and OPP are used for bottles, jars, crisp packets, biscuit wrappers and boil-in-bag films among many other applications.

Polyethylene terephthalate (PET) is a very strong transparent glossy film which has good moisture and gas barrier properties. It is flexible at temperatures from
-70ºC to 135ºC and undergoes little shrinkage with variations in temperature or humidity.
Low-density polyethylene (LDPE) is used as a copolymer in some tubs and trays.
LDPE film is heat sealable, chemically inert, odor free and shrinks when heated. It is a good moisture barrier but has a relatively high gas permeability, sensitivity to oils and poor odor resistance.

High-density polyethylene (HDPE) is stronger, thicker, less flexible and more brittle than low-density polyethylene and has lower permeability to gases and moisture. It has a higher softening temperature (121ºC) and can therefore be heat sterilized.

Uncoated polyvinylidene chloride (PVdC) film has very good moisture, odour and gas barrier properties. It is fat resistant and does not melt in contact with hot fats, making it suitable for freezer-to-oven foods. PVdC is also used as a coating for films and bottles to improve the barrier properties.

Polystyrene is a brittle clear sparkling film which has high gas permeability. It may be oriented to improve the barrier properties.
Ethylene vinyl acetate (EA) is low-density polyethylene, polymerized with vinyl
acetate. It has high mechanical strength, and flexibility at low temperatures. EA is as flexible as PVC without plasticizers, has greater resilience than PVC and greater flexibility than LDPE.

Paper and board

Paper has a number of advantages as a food packaging material:

• it is produced in many grades and converted to many different forms, especially boxes or cartons

• it is recyclable and biodegradable

• it is easily combined with other materials to make coated or laminated packs

• it can be produced with different degrees of opacity.
  Kraft paper is a strong paper which is used for 25 50 kg multi-wall sacks for powders, flour, sugar, fruits and vegetables. It can be bleached white, printed or used unbleached (brown). It it usually used in several layers or plies, to give the required strength.
  Paperboard is a generic term covering boxboard, chipboard and corrugated or solid fibreboards. Typical paperboard has the following structure:

• a top ply of bleached pulp to give surface strength and printability

• an underliner of white pulp to stop the grey/brown colour of middle plies showing through middle plies of lower grade material

• a back ply of either low grade pulp or better grade pulp if strength or printability are required.
  All plies are glued together with hot-melt or aqueous adhesives.

References:
Fellows, P. 2000. Food Processing Technology, Principles and Practice, 2nd Ed., CRC Press, England

http://www.bpf.co.uk/ 
http://www.rapra.net/ 

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Migration term could be defined as mass transfer from an external source into food by sub-microscopic processes or mass transfer from an external source into food in physical contact with it by sub-microscopic processes
The meanings of other parts of the verb 'to migrate' follow from the above definitions. Migrants describe the substance which undergoes migration in a particular situation. 'Potential migrant' can be used to describe the substance in anticipation of a migration situation arising.
The substance of migrating may be one or more individual chemical species. If migration of a single chemical species is measured, the result is called specific migration, abbreviated to SM (mainly in the context of specific migration limit, abbreviated to SML). If a group of chemical species is measures, the total may be called group migration and if the intention is to determine total migration. The second of these, abbreviated to OM.
'Simulants', 'Food Simulants (FS)' or 'Food Simulating Liquids (FSL)' is used both in research and regulatory control to estimate migration where tests with real foods present difficulties. This is, in fact, more the rule than the exception and hence more studies are done with FS than with real foods. The obvious requirement for a FS is that is should mimic the interactions between the foods. It is intended to simulate and the M/A (a material, article or any solid structure in contact with food and capable of giving rise to migration from itself into the food abbreviated to M/A) under test (i.e. from which migration occurs) at least in all respects affecting migration. Real foods extend over a large range of chemical species and are subject to substantial variations in composition. Moreover, traditional official classifications of foods, such as are used for food control regulatory or surveillance purposes, relate more to nutritional properties than the physicochemical ones which control migration. So the mimicry is far from perfect.
From the definitions given above, migration is not a basic science; and it deals with too narrow a specialization to be generally regarded as an applied science (such as agricultural chemistry or food science). Although potential migration into food must be taken into account when developing new packaging and other food contact systems. It is not a basis for design which could be developed into a new technology.
A particular complication for the study of migration into food is that, although migration is predominantly a physical process, the majority of studies in the field call for the skills of analytical chemistry. For health safety(toxicology) studies, the main basic skill required is biology (there are others) which does not enter significantly into migration at all.

The main factors of chemical migration

The packaging material is the source of any chemical migration. The extent of any chemical migration depends first on the concentration of the chemical in the packaging. If a substance is not present in a packaging material then it cannot migrate. If a substance is present in the packaging then, other things remaining equal, migration levels will be higher if the concentration in the packaging is increased and vice versa.

This depends on the physical properties of the food and the size and shape of the pack. Another factor that determines the nature and extent of any contact with the food is the presence of a barrier layer. If the chemical that may migrate is located in one layer of the packaging material but this is separated from the food by an intervening layer, then this barrier layer - between food and chemical migrant - may retard or prevent migration from occurring. This is quite a common situation with modern multi-laminate packaging materials where inks, adhesives, or one or more of the laminate plies do not touch the food directly.

The nature of the food that touches the packaging is important for two reasons:
Incompatibilty
If the packaging is not compatible with a given type of food then there can be a strong interaction leading to an accelerated release of chemical substances. Examples are the interaction of fats and oils with certain plastics that leads to swelling of the plastic and leaching of substances from the plastic. Leaching, formally known as Class III migration, occurs because the diffusivity of the plastic increases with any swelling. This means that with swelling, the plastic starts to behave more like a fluid. An even more extreme example of an undesirable interaction between packaging and food is the corrosion of uncoated metal surfaces leading to high metal release into certain acidic foods, or the leaching of heavy metals from ceramic glazes. It is important to avoid such obvious mismatches and ensure that packaging materials are compatible with the food that it is intended to pack.
Solubility
The nature of a food has a pronounced influence on chemical migration because it determines the solubility of any packaging chemical in that food. This influences the amount of migration that may occur. Foods are conventionally classified into five categories: aqueous, acidic, alcoholic, fatty, and dry.

The migration of chemicals is like virtually all chemical and physical processes in that it is accelerated by heat. So migration will occur faster if the temperature is raised. Packaging materials are increasingly used under a very wide range of temperature conditions, ranging from storage deep frozen, refrigerated and at ambient temperature, to boiling, sterilization, microwaving and even baking in the pack. Clearly, a material suitable for one particular application may not necessarily be suitable for another.

Materials suitable for short duration contact may not be suitable for longer service times. The kinetics of migration is, to a first approximation, first order in that the extent of migration increases  according to the square-root of the time of contact: M? t1/2. The time (duration) of contact for common packaging can very enormously:

• minutes (e.g. take-away foods)

• hours (e.g. fresh bakery, sandwiches)

• days (e.g. fresh milk, meat, fruit and vegetables)

• weeks (e.g. butter, cheese)

• months and years (e.g. frozen foods, dry goods, canned foods, drinks)

Mobility of the chemicals in the packaging
The mobility of a chemical in the packaging material depends on the size and shape of the molecule, any interaction it experiences with the material, and the intrinsic resistance to mass transfer that the material presents. It is assumed that the chemical is compatible with the material. If the chemical is not compatible with the material then it could 'bloom' to the surface and give enhanced migration. To provide a general understanding, it is helpful to consider three general cases: impermeable materials, permeable materials and porous materials.

Impermeable materials
These are exemplified by 'hard' materials such as metals, glass and ceramics. The material is an absolute barrier and there is no migration from the interior. Migration is confined to a surface phenomenon only.

Permeable materials
These are exemplified by 'plastic' materials such as plastics, rubbers and elastomers. The materials offers some limited resistance to migration but this can occur not only from the surface but also from the interior of the material. The resistance to mass transfer depends on the structure, density, crystallinity, etc., of the material.

Porous materials
Exemplified by paper and board materials with a heterogeneous, open network of fibres with large air spaces or channels. Low molecular weight substances in particular can migrate rather rapidly with little hindrance offered.

Migration increases with:

• increased duration of contact

• increased temperature of contact

• higher levels of the chemical in the packaging material

• surface area of the contact

• aggressive foodstuffs.

Migration decreases with:

• higher molecular weight substances in the packaging material

• only dry or indirect contact

• low diffusivity ('inert') packaging materials

• presence of a barrier layer.

References:

"Migration From Food Contact Materials", Edited by L.L.Katan, First Edition 1996, Published by Blackie Academic & Professional, an imprint of Chapman & Hall, London.

"Chemical Migration and Food Contact Materials", Edited by K.A. Barnes, C.R.Sinclair and D.H.Watson, First Edition 2007, Published by Woodhead Publishing Limited, England.

http://crl-fcm.jrc.it/
http://www.speciation.net/Public/Links/DB/Links/detail.html?id=1447
http://www.foodcontactmaterials.com/

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In the European Union two types of legislation exist for food contact materials: Community legislation which is adopted by the EU and national legislation adopted by the Member States. The European Union aims, amongst other things, at establishing an internal market and economic union.

In the area of food contact materials the first Community legislation was adopted in 1976 laying down the general principles in a Framework Directive. At that time national legislation on food contact material and articles existed in the Member States but provisions were divergent and thus were posing a barrier to trade. The adoption of the framework Directive was a first step in harmonization of the food contact materials legislation. In the meantime specific Community legislation on food contact materials has been adopted but not in all areas.

big grafic

The community legislation comprises general rules applicable to all materials and and articles laid down in the in the Framework Regulation and specific rules only applying to certain materials or certain substances. The two general principles on which legislation on food contact materials is based the principles of inertness and safety of the material. A general overview is presented in Figure 1.

The harmonisation at EU level of the legislation on food contact materials fulfils two essential goals: the protection of the health of the consumer and the removal of technical barriers to trade.

Food contact materials should be safe and should not transfer their components into the foodstuff in unacceptable quantities. The transfer of constituents from food contact materials into food is called migration. To ensure the protection of the health of the consumer and to avoid any contamination of the foodstuff two types of migration limits have been established for plastic materials:

• an Overall Migration Limit (OML) of 60mg (of substances)/kg (of foodstuff or food simulants) that applies to all substances that can migrate from food contact materials to foodstuffs,   and

• a Specific Migration Limit (SML) which applies to individual authorised substances and is fixed on the basis of the toxicological evaluation of the substance. The SML is generally established according to the Acceptable Daily Intake (ADI) or the Tolerable Daily Intake (TDI) set by the Scientific Committee on Food (SCF). To set the limit, it is assumed that, every day throughout his/her lifetime, a person weighing 60kg eats 1kg of food packed in plastics containing the relevant substance at the maximum permitted quantity.

Food contact materials and articles are regulated by

• The Framework Regulation (EC) No 1935/2004 sets up general requirements for all food contact materials

Framework Regulation (EC) No 1935/2004
The harmonisation at EU level of the legislation on food contact materials fulfils two essential goals: the protection of the health of the consumer and the removal of technical barriers to trade. Food contact materials should be safe and should not transfer their components into the foodstuff in unacceptable quantities. The transfer of constituents from food contact materials into food is called migration. To ensure the protection of the health of the consumer and to avoid any contamination of the foodstuff two types of migration limits have been established for plastic materials:

• an Overall Migration Limit (OML) of 60mg (of substances)/kg (of foodstuff or food simulants) that applies to all substances that can migrate from food contact materials to foodstuffs,   and

• a Specific Migration Limit (SML) which applies to individual authorised substances and is fixed on the basis of the toxicological evaluation of the substance. The SML is generally established according to the Acceptable Daily Intake (ADI) or the Tolerable Daily Intake (TDI) set by the Scientific Committee on Food (SCF). To set the limit, it is assumed that, every day throughout his/her lifetime, a person weighing 60kg eats 1kg of food packed in plastics containing the relevant substance at the maximum permitted quantity.

Legislation on specific materials covering groups of materials and articles listed in the Framework Regulation"
Currently the legislation on specific materials concerns the legislation on ceramics, regenerated cellulose film, plastics and recycled plastics.

Ceramics are regulated by Council Directive 84/500/EEC as amended by Directive 2005/31/EC. The Directive sets migration limits for cadmium and lead which might be released from decoration and/or glazing. It gives an analytical method for the determination of the migration of these substances.

Regenerated cellulose film is regulated by Commission Directive 2007/42/EC of 29 June 2007 that is a codified version of 93/10/EEC and 2004/14/EC. This Directive sets a positive list of authorised substances and the conditions under which they can be used and includes provisions for plastic coated regenerated cellulose film.

Safety Aspects

There can be absolutely no doubt that food packaging has greatly improved human health both new and through the ages by helping to provide regular and reliable supplies of safe, wholesome and nutritious foods. But chemical migration is always undesireble and if not controlled it could be hazardous to the health of consumers.The exception is for 'active packaging' which may be intended to release substances into the food beneficial effects, such as antioxidants or preservatives.

The main health concern are for possible effects from chronic (i.e.long-term) exposure to migrating substances. There are two specific exceptions to this, where an accute effect may arise. One is migration of tin from tinplated steel into (especially) canned tomato products where high tin concentrations in food may cause short-term stomach upsets in some people but without any lasting harm. The other concern latex allergen transfer which could have serious implications for some individuals. Recent research sponsored by the UK Food Standards Agency has shown that latex allergans may be present in some food packaging  materials and that there is a theoretical possibility of transfer from the material to the food. The materials include cold seal adhesives based on latex and latex food handling gloves. Further work is being done to improve methods to detect and quantify latex allergans in packaging and foods, to see if these allergens do migrate into food.
To address possible long-term health concerns, the risk assesment process involves describing the toxicological hazard profile of the chemical substances, using qualitative and quantitative data, and coupling this to an estimate of exposure to a chemical migrant, to assess any risk. Consequently, the information that is required on packaging chemical comprises data on (i) toxicity, and (ii) dietary exposure. As a general principle, the higher the exposure the more toxicological information is required.
http://www.bfr.bund.de/cd/528
http://www.dfvf.dk/
http://ec.europa.eu/dgs/jrc/index.cfm?id=4070&lang=en
http://www.nzfsa.govt.nz/imported-food/testing/heavy-metals/index.htm

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Modified Atmosphere Packaging (MAP)

Modified atmosphere packaging (MAP) is a technique used to prolong shelf-life and maintain the quality of foods by altering the composition of atmosphere inside the packages. The composition of gas mixtures used for this purpose depends on the food and the nature of deterioration mechanisms. Deteriorative reactions of food can be of biochemical, physiological, physical and microbiological origin. In MAP systems O2 concentration is usually kept at low levels in order to reduce the rate of oxygen dependent undesirable (oxidative) reactions and to reduce the growth of aerobic microorganisms. Elevated CO2 is mostly used due to its bacteriostatic effects and nitrogen is used as balance gas. In some cases noble gases and high O2 concentrations can also be used (high oxygen modified atmosphere packaging) in MAP systems.

ve/veya karbondioksitçe zengin atmosferler kullanılır.

MAP of fresh fruits and vegetables is a more laborious issue. The reason is that fresh produces are living organisms therefore they continue to respire even after harvest in order to produce energy for vital biological reactions. As a result when fresh fruits and vegetables are put in packs they naturally modify surrounding atmosphere by consuming O2 and producing CO2 (passive MAP). Since anoxic conditions leads to fermentation, complete consumption of oxygen should be avoided by selecting packaging materials permitting O2 to enter and CO2 to leave the package. In MAP of fresh produces another concern is the accumulation of ethylene in packs. Ethylene is a natural plant hormone which regulates numerous physiological reactions. Its physiological impact is more prominent on climacteric f&v such as avocado, melon, tomatoes, broccoli; apricot etc. The reason is that exposure of these commodities to exogenous ethylene accelerates their ripening thus diminishes their shelf-life. In some other cases ethylene may cause physiological disorders as well i.e. russet spotting on iceberg lettuce, yellowing of cucumbers. Therefore keeping ethylene concentration at low levels is mandatory in order to prolong shelf-life of ethylene sensitive produces. For this purpose, generally atmospheres which are poor in O2 or/and rich in CO2 are used due to their retarding effect on ethylene production.

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New Packaging Technologies

Active Packaging
Active packaging is a term used to describe packaging systems whose performance has been improved by incorporating auxiliary components in packaging material or in the head space. Main commercial applications of active packaging include O2 absorbing pads and sachets used to create either oxygen free or low oxygen atmospheres, CO2 absorbing pads and sachets used to remove CO2 in packs i.e. roasted coffee, ethylene adsorbing pads and sachets used to remove ethylene in packs of ethylene sensitive fresh produces, moisture absorbing pads and sachets used to avoid excess moisture accumulation in packs i.e. flesh meat, sliced tomatoes and ethanol emitting pads and sachets used to control microbial growth. Although all these auxiliary components are effectively used in food industry, due to their drawbacks such as consumer rejection and their incompatibility with liquid foods, there is an increasing trend for incorporating all these functionalities (and some other functionalities such as anti-oxidant release, flavor odor absorbers) in packaging materials. However until now only packaging materials with O2 scavenging and antimicrobial properties have been successfully commercialized.

Intelligent Packaging
Intelligent packaging can be defined as systems which are capable of monitoring the condition of packaged foods to give information about the quality of the packaged food during transport and storage. Main difference of intelligent packaging from active packaging is that intelligent packaging systems give information about the history and quality of packed food product whereas active packaging systems has a goal to minimize the factors which are deleterious to product quality.  TTI's (Time Temperature Indicators), RFID's, gas concentration indicators, ripeness indicators for fruit&vegetables and microbial quality indicators can be counted as some commercialized examples of intelligent packaging systems. 

Nanotechnology Applications
Packaging is traditionally used to extend the shelf life of food and maintain its quality by inhibiting the migration of moisture, oxygen, carbon dioxide, aromas and lipids. The main purpose of food packaging is to protect the product from the surroundings. The Food and Beverage industry is always seeking new technologies to improve quality, shelf life, safety and traceability of their products. The advent of nanotechnology, that involves manufacture and use of materials in the size range of up to 100 nanometers in one or more dimensions, has opened up new opportunities for the development of new packaging materials with improved properties for use as food contact materials.
The incorporation of certain nanomaterials into polymers has been reported to improve mechanical and/or barrier properties, which is of great interest for applications in food packaging. This is because there has always been a need for improved packaging materials to control certain degradation processes in foods (e.g. rancidity of fats and oils, degradation due to microbial growth) through the control of diffusion of oxygen. The addition of certain nanoparticles into shaped objects (e.g. bottles, containers), and other forms of packaging (e.g. films) can render them light, fire resistant, and stronger in terms of mechanical and thermal performance, and may also make them less permeable to gases. For example, improvement in properties of certain nanomaterial-polymer composites has been reported with regard to durability due to increased strength, temperature resistance, flame resistance, barrier properties, optical properties, processability due to lower viscosity and recycling properties.

The following main nanotechnology application categories for food contact materials:

• Food contact materials incorporating nanomaterials to improve packaging properties (flexibility, durability, temperature/moisture stability)

• 'Active' food contact materials that incorporate nanoparticles with antimicrobial or oxygen scavenging properties

• 'Intelligent' food packaging incorporating nanosensors to monitor the condition of the food

• Biodegradable polymer-nanomaterial composites

Microparticles may enter the gut mainly through ingestion of food and drinks. However, very little is known about the dietary toxicity of microparticles in the gut, and even less about the toxicity of nanoparticles (Tran et al, 2005). The main consumer safety implications from a nanotechnology-derived food packaging would be intrinsically linked to the physicochemical properties of nanoparticles, and the likelihood and level of exposure from migration into food and drinks from food contact materials or active surfaces.
Very few studies have been carried out so far into the toxicology of nanoparticles, and their potential harmful effects in biological systems are therefore largely unknown. There is concern that exposure to some of the engineered free nanoparticles may pose unforeseen health or environmental hazards. Despite claims over the antimicrobial effects of a number of engineered nanoparticles, such as nanosilver, there is currently no published research on the effect that food/ drinks, contaminated due to migration of nanoparticles from packaging, may have on the gastrointestinal tract or on the natural gut microflora. Also, whilst there is some evidence on the potential of certain nanoparticles to cause harm, the likelihood and extent of the consumer exposure due to migration from food contact materials into food and drinks is currently unknown. It has also not been known whether the incorporation of nanomaterials into plastic polymers would lead to a greater migration of non-nano components.
There are a number of major knowledge gaps that require further research; for example, to understand the behaviour, fate and toxicology of nanoparticles, their interactions with other food components in the gastrointestinal tract, effects on the function of gut epithelium and other cells, and on the natural gut microflora.

References
Chaudhry Q., Scotter M., Blackburn J., Ross B., Boxall B., Castle L., Aitken R, Watkins R., 2008. Applications and implications of nanotechnologies for the food sector. Food Additives and Contaminants, March 2008; 25(3): 241-258.

Chaudhry Q., Castle L., Bradley E, Blackburn J, Aitken R, Boxall A., 2008. Assessment of current and projected applications of nanotechnology for food contact materials in relation to consumer safety and regulatory implications. Food Standard Agency Report, UK.

Tran C.L, Donaldson K, Stone V, Fernandez T, Ford A, Christofi N, Syres J.G, Steiner M, Hurley J.F, Aitken R.J and Seaton A (2005) A scoping study to identify hazard data needs for addressing the risks presented by nanoparticles and Nanotubes; DEFRA Research Report

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