Food Packaging

azaquar's picture
Submitted by azaquar on Wed, 11/05/2011 - 16:00

Presentation

Historically, man has used the containers of skin, leaves, gourds, baskets, wood, pottery and, from 1500 BC. BC, the glass containers to protect food.

With scientific developments and recent technological advances particularly in terms of food preservation, food packaging industry has grown steadily for a part, follow these developments, and secondly, to meet the growing the consumer.

Today, there is a myriad of food packaging that have functions beyond the protection of food (seduction, meet regulatory requirements, etc.).. The materials used are also diverse, we find simple materials like wood, glass, metals, but also complex materials involving several materials at once.

The aim of this paper is to review different functions qu'assurent food packaging and presenting the main materials used in their manufacture.

Definition:

Food packaging: Material mono or multilayer for containing a food while ensuring its safety until it is consumed.

Role of food packaging

Food Preservation

Conservation is to maintain as long as possible, the highest level of "quality" of the food, acting on various mechanisms of deterioration to slow or eliminate the effects.

The preservation of food, resulting in a successful optimization between contradictory imperatives whose implications are difficult to reconcile: duration (imperatives of marketing and distribution), scientific and technological factors (incorporating research and development), cost (requirements economic and commercial), quality of the food (regulatory requirements, branding, consumer demands).

Packaging can provide simultaneously passive protection and / or active food: We are talking about passive protection when the package is to feed a physical barrier against the deterioration factors (O 2, humidity, ...). As for active protection, it is present when the package may react with the environment where the product is exposed as is the case, for example, packages containing UV absorbers designed to protect sensitive foods such radiation.

Qualitative dimensions of a food

If AFNOR broadly defines quality as "the ability of a product or service to satisfy the needs of users" (AFNOR standard NF-X-50-109), it is necessary in the case of Food, distinguished in this multi-faceted global concept all correspond to characteristics alterable over time and are all closely related to storage conditions:

  1. hygienic quality: the safety of the food in her normal job is an absolute requirement. The food should contain no toxic elements at levels dangerous to the consumer, dosages of the evaluation includes the frequency of consumption, the intake and the concept of "acceptable daily intake". The hygienic quality may be compromised by biological, chemical or physical.
  2. nutritional quality is the ability of the food to feed well. It includes:
  3. one hand, a quantitative aspect: energy stored in chemical form (starch, lipids), measured by calorimetry, or loss by consumption competitive with other living beings for molds, insects, rodents;
  4. secondly, a qualitative (nutritional balance of food to the needs of the consumer: amino acids, vitamins, minerals, ...).
  5. sensory or organoleptic quality: This component of the hedonic quality is very important, but subjective and variable in time and space, depending on individuals and their cultural references. This includes quality taste sensations, olfactory, tactile, visual or auditory (eg, crackle bread) well defined. This component is extremely sensitive to storage conditions and therefore packaging. Indeed, storage misbehaved, improper packaging can cause the appearance of unpleasant taste (taste musty, fusty, rancid fermented ...), odor (musty smell), or changes in consistency (hardening, liquefaction, ...).

Environmental factors or external environmental factors

The qualitative and quantitative factors of the environment depend on the cause or causes of deterioration that can express themselves and to be predominant in a particular conservation process, and the speed of weathering reactions they cause.

The different factors that play a role in altering the following:

  1. the "time factor" introduced the concept of reaction rate, whose knowledge is essential to determine the maximum probable conservation. This time factor is reflected in practice by the deadline or recommended for consumption or sale on the packaging of food products.
  2. factors "temperature" and "heat" (energy available) are of course extremely important: an increase in temperature, which is a measure of the increased molecular agitation, reflects an increase of kinetic energy and the probability of collisions between molecules. When the bustle and energy become available sufficient for certain bonds are broken (including hydrogen bonds), it produces changes in macromolecular structures.

The temperature is also the key parameter of stability or changes in thermodynamic equilibrium. Thus, the stability of physical states (emulsions, gels, liquid states / solid, crystalline state, amorphous state) depends essentially on the temperature, and to a lesser extent the factors pH, a w, etc..

Temperatures are well preserved and displayed on the container must be respected by all actors in the food chain.

  1. The hygroscopicity is measured in particular by the "sorption curve" which expresses the equilibrium thermodynamics, the relationship between on the one hand, the water content of the substance, and secondly, the activity of water (a w) of the said substance. Hygroscopic exchanges are obviously encouraged by the state division of the system air / food upon which the exchange surfaces, and thus the transfer speed.
  2. the factor "pH" greatly influences the enzymatic activities and microbial growth; acidic environments is generally conducive to good conservation.
  3. the factor content of oxygen and carbon dioxide (atmospheric composition in equilibrium with the food) comes on the nature of metabolism (aerobic or anaerobic) microorganisms and living entities, and not the intensity of oxidative enzymatic reactions and selected enzymatic oxidation.
  4. factor "mechanical stress (pressure, shock, various constraints) may be responsible for deformation, crushing and / or breakage that confer a crippling aspect to the product.

Considering these environmental factors and their role in the revelation or suppression of the causes of deterioration, we can understand the vital role played by the packaging which is primarily a barrier between an internal environment (the food product and its causes intrinsic alteration) and the external environment bearer of "environmental factors" (Figure 1).

Thus, conditioning and packaging of food products are an integral part of the panoply of techniques used to lengthen the product life (sterilization, cold, drying, smoking, salting, additives, ...) and are often closely associated with one of these techniques they are the indispensable (eg, storage under inert gas free of oxygen is associated with the choice of packing porosity determined these gases).

Safety and inertia of the pack

If the need for the safety of the package vis-à-vis the food may seem obvious, it is obtained in practice is not necessarily simple, because the package may itself be a source of contamination Accident and conservation. The continuing complexity of the packages, which include several components, often of different nature (plastics, foil, paper and board), a presentation and a more sophisticated look (design, colors) that requires the implementation of many chemicals (inks, varnishes, solvents), greatly increases the risk of migration of volatile substances (including solvents) or soluble, since the packaging to the food it contains.

These contaminants can be toxic (lead or tin cans, vinyl chloride monomer in plastic bottles, for example), or may alter the organoleptic properties of the food by its taste or smell unacceptable. It is in this respect, positive list of substances it is lawful to incorporate packaging (ink, paint, etc..).

Migration can indeed take 3 to 4 weeks before the organoleptic defect is noticeable, a period equal to that usually requires distribution and marketing of the product. Thus, sensory impairment falls completely to the usual quality checks performed on the product (including a tasting panel), and are increasingly the norm in the plant: the manufacturer can not therefore be alerted that by the first consumer complaints, that is to say 6-8 weeks behind the manufacturing period during which the manufacture and packaging in the packaging defective have continued at a rate of several tens of tons or tons per day.

It must then be recovered, in warehouses and distribution networks, and destroying tens or hundreds of tons of tainted products: the financial and commercial direct damage and indirect damage (deterioration of the image, loss of market shares) are still huge and sometimes fatal for a company. In addition, the establishment of responsibilities is often difficult because of the time elapsed and the lack of significant sample at the time and expertise. The relative frequency of this type of disaster can only encourage very strongly advise food manufacturers, is to establish quality control of packaging upon receipt of each new batch, by systematically testing enabling detect in real time, ie before use, not inertia of the packaging or related products (glues, varnishes, inks, etc..) or to implement a seamless system of quality assurance with their packaging supplier.

We can not advise either too to store the new packaging in a clean, dry place, because contamination of the package may also be at the user.

Role of passive protection packaging

The packaging is primarily a barrier between the product and the external environment, and therefore passive protection vis-à-vis the environment. From this point of view, we can also consider that the skin of some fruits (banana, orange ,...), the shell (walnuts) or shell (egg) is already naturally occurring forms of packaging.

  • Mechanical protection:

Mechanical protection is the primary function of any package, in fact, the food, depending on their physical condition should be protected:

    1. against the transfer of momentum, during handling and storage, that is to say: against instantaneous shocks may break or crack the brittle products such as eggs, pastries, sweets or against constraints more or less permanent may distort the texture products pasty or soft plastic products (pasta, fats such as butter or margarine, cheese, yogurt, etc.)..
    2. against the flow of liquids, which may appear during welding or closures (caps) that do not hold enough or the constraints on the occasion of collisions with objects that could pierce the package.
    3. against insects that may pierce the cardboard packaging and plastic to break into the product, and whose ravages can be considerable, especially in tropical countries.
  • Protection against transfer of material:

Transfer of liquids (waterproof): The problem of waterproofing and sealing (especially welding) to liquid products mainly arises for new packaging materials, simple or complex associated with polyethylene and cardboard to aluminum metallized films used for milk and beverages.

Transfers of gas: No material, except perhaps the welded metal box and jar glass closure called "bobbin" and overlooked, is strictly gas-tight. Indeed, most of the materials (cardboard, foil, plastic variety) have a porosity greater or lesser gases. In view of these gas transfer, packaging plays a dual role:

  1. On the one hand, a role of blocking the transfer from outside to inside the package:
    1. barrier for oxygen and water vapor for the protection of sensitive products to oxygen (risk of mold growth or aerobic bacteria; risk of oxidation or rancidity), or subject to the rehydration (risk alteration of texture: loss of crispy biscuit or toast, for example, risk of formations saturated with sugary or salty and risk of starting the mold by increasing a w of the product);
    2. Dam also for all the volatiles can be present in the environment (oil, smoke, perfume, ...) and might alter the organoleptic properties (taste, smell) of food.
  2. On the other hand, a role of blocking the reverse transfers, from inside to outside to avoid:
    1. flight specific flavors of the product;
    2. dehydration product, when the formulation is that of a moist or semi-wet (prepared foods, intermediate moisture);
    3. leakage of gas or gas mixture that could be introduced within
      packaging to preserve the product (CO2, N2, etc..).

The gas seal is never total, a choice must be made between the types of materials or material combinations to achieve the desired objective while taking into account:

  1. Nature of product;
  2. Conservation mode (cold, hot ,...);
  3. Storage conditions and product distribution;
  4. Shelf life.
  5. Protection against transfer of energy

Two types of energy transfer can occur from the external environment to the product through the package (one of whose roles will be to oppose it), and trigger or accelerate chemical or microbiological spoilage.

  • Transfer of radiant energy: Light

Many products are found to be sensitive to light (visible and near IR or UV) initiates photochemical reactions between other leaders of color changes, loss of vitamins A and C. For these products, the photoprotective role of packaging is either to filter out harmful wavelengths, while revealing the product, or stop any light input as to the opaque packaging which is compensated for in general the lack of vision produced by an appropriate image printed on it. Many studies have been done on the role of light on alteration products including yogurt, juices and oils.

  • Heat transfer (radiation, convection and conduction)

Many products for their preservation a relatively stable temperature. The package contributes to the conservation of frozen products in opposing the warming of the product during transport and handling of various faults and storage devices.

Good thermal insulation properties are also popular for packaging products delivered hot.

In a more general character insulating a package is a useful feature when the container is subjected to temperature gradients, parts of which can then undergo a localized increase in temperature and water content to achieve values ​​exceeding the critical thresholds of preservation. Conversely, excellent heat conductivity is desired for the boxes used in the batch sterilization.

  • Protection against microorganisms in the atmosphere

Maintaining hygienic and microbiological quality of food is one of the primary roles of food packaging. On the one hand, it constitutes a physical barrier between the packaged products and microorganisms in the air. On the other hand, it limits or prevents gas exchange may favor the development of flora still contained in the food.

Four cases must be distinguished:

  1. That of non-sterile products (biscuits, breads, candies ,...) bit alterable in principle by the microflora (dry or protected by a preservative): packaging avoids excessive contamination, or the contribution of pathogens by persons required to handle the products.
  2. That products containing a specified plant, which should not be contaminated by germs competitive foreigners may be substituted for the original flora (cheese, yogurt, sausages).
  3. One product, which without being sterile, require extremely rigorous hygiene (meat, fish, vegetables) to prevent product contamination by pathogenic or spoilage flora.
  4. Sterile products (eg milk sterilized) including packaging, in addition to the absolute seal to all microbial organisms must withstand sterilization conditions, or be suitable for the aseptic conditions.

Examples:

Example 1: Canning.

Glass jars and cans used for canned foods offer several advantages:

  1. perfectly tight to liquids, gases and micro-organisms;
  2. resistant to heat treatment undergone;
  3. allow for expansion and contraction of the atmosphere inside the container during heating and cooling, without breaking or bursting: the role of deformable lid metal cans, or the rubber gasket to the glass jars.

Example 2: Aseptic.

In this technique, which applies mainly to liquid (milk, juice) but can also be considered for solids, the bulk freshly sterilized product, is introduced aseptically into a sterile packaging itself. The vessel is most often formed continuously in the packaging machine itself: it is either a complex film based flexible cardboard, or plastic film, directly shaped, welded and filled and sterilized immediately closed or extruded plastic containers at high temperature immediately filled and sealed.

Protective role of active packaging ("active" or "intelligent" packaging)

According to the Regulation of the European Parliament and Council No. 1935/2004 of 27/10/2004: "the active materials and articles intended to prolong life or to maintain or improve the condition of packaged food. They are designed to deliberately incorporate components that would release or absorb substances into food packed in the environment or food. "

The trend goes beyond the passive role of food packaging as an inert barrier between the food and the outside environment, but part of the process of preparation and storage of food. This package called "active" or "smart" respond to changes in the external environment and interacts with the product.

Special packaging is sometimes made to meet very specific needs. These active packaging can monitor the trade:

  1. Oxygen,
  2. Carbon dioxide,
  3. Humidity,
  4. Ethylene,
  5. Aroma
  6. Pressure.

This is the case, for example, bags with a valve permitting the evacuation of the pressure created by the release of gases into the roasted coffee.

Another example is:

  1. The conditioning oils in glass shaded to protect content against photo-oxidation caused by ultraviolet (UV) or even packaged in clear glass containing the components absorbing UV rays;
  2. Packaging in packages containing ascorbic acid known for its antioxidant properties and
  3. Packaging in containers containing silica gel with its activity to absorb water vapor and thus reduce the humidity around the product and can alter it.

Information Functions

To be fair, the information conveyed to the consumer must be legible, understandable, correct, accurate and not confusing.

The packaging, vehicle information fair

Information understandable by the consumer

Understandable information is information in a language accessible to consumers, an example is the decree of June 2002 labeling that makes the Arabic language compulsory labeling of food in Morocco.

Honest information

In fairness, it refers to the use of advertising or misleading claims or even misinformation that may mislead the consumer and therefore affect their choice of product.

The packaging, vehicle full information

To make an informed choice, it is not enough information given to consumers are fair. It is essential that it has full information about the essential characteristics of products that allows it to make comparisons between products presented under the same name.

Packaging vehicle qualitative information

The consumer wants to be able to clearly identify the origin and quality of the product he buys. It is also more frequently food-health link.

Signs of quality is one way to inform consumers about the quality of a product. These signs allow the producer a price for their product and also allow the consumer to know generally the product's origin and the conditions of manufacture.

These signs are now very numerous (Appellations of Origin, designations of origin, agricultural labels, ...).

Marketing functions of packaging

We distinguish the following main functions:

  1. "Tracking" and "identification": the first level contact between the consumer and the product on the shelves of supermarkets.
  2. "Information" and "seduction" which will first inform consumers, attract and encourage the purchase.
  3. Finally when the product is the consumer, the packaging will still function as "service" via its user manual.

The "tracking"

The first difficulty for the consumer in locating the most it lies between other competing products, it must be truly remarkable to be identified before the others.

The "identification"

It is necessary that the packaging may allocate the proceeds to its universe of reference and thus allow the consumer to identify the product without any confusion. It cites as examples:

  1. Milk cartons or juice can not really be confused because the juice blocks are much more richly printed than milk.
  2. A glass jar keeps suggesting "tradition" and looks less industrial than metal tin can.

The "seduction"

The seduction of the consumer is one of the most subjective and most important of the package.

The "service"

This last feature appears in fact that after the purchase, the consumer. It includes all the usual qualities or facilities that job must have a package for the consumer and the guarantee of inviolability of the product. To illustrate this feature, it cites as examples:

  1. Plugging security for hazardous household products.
  2. The ability to easily reseal the product after use as a first for UHT milk.

The "handling"

Here is the practical aspect of the package to the distribution that prevails. A choice of packaging material and its shape allows good protection of the product during handling from production to final consumer.

The "recovery"

The question of optimization requires the manufacturer to choose a form of packaging that allows to maximize the space allocated to the product in a supermarket that can generate a good return while minimizing the space occupied.

The different packaging materials

Glass

Glass is an inorganic material based on silicon, manufactured from silica sand. It is used as food packaging and has several important advantages:

  1. Transparent;
  2. Inert;
  3. Reusable;
  4. Recyclable.

However, it contains some major drawbacks that can be enumerated as follows:

  1. Fragile;
  2. Dangerous;
  3. Low thermal conductivity.

Uses

The use of glass as a packaging material in food dates back many centuries. The glass packaging includes bottles, cans, jars, cups, etc..

Foods packaged in glass are numerous:

  1. Liquids: Water, water, juices, oils and soft drinks, milk, oils, vinegars, ...
  2. canned vegetables, fruit, pies, meats, ...
  3. jams, honey, spreads, ...
  4. condiments, mustard, seasonings, ...
  5. baby foods.
  6. milk products: yogurt, ...
  7. soluble coffee, spices, ...
  8. meals, etc..

Intrinsic quality of glass packaging

The extensive use of glass in the food sector is not by chance but is fully justified by a set of qualities to glass, the most important are listed below:

  1. Glass is impervious to gases, vapors and liquids. It is an exceptional barrier material.
  2. Glass is chemically inert vis-à-vis food and liquids and is not a compatibility problem and may be used for all food products in liquid, solid, paste or powder.
  3. Glass is an inert material, hygienic and bacteriological terms, it does not fix and does not promote the growth of bacteria or microorganisms on its surface.
  4. Easy to clean and sterilize.
  5. The glass has no smell and does not pass the taste and do not change and is the guarantor of the organoleptic properties and flavor of the food.
  6. The glass is transparent and allows a visual check of the product.
  7. It can be colored and thus provide protection against ultraviolet rays can damage the product inside.
  8. The glass is resistant to high internal pressures that make him undergo some liquids.
  9. The glass has sufficient strength to withstand the shocks on packaging lines working at a high rate and to withstand significant vertical stacks for storage.
  10. It is recyclable.
  11. Passes and permits microwave heating of food.

Metallic materials

Steel base material: Tin plated iron and

The main material for tins is the tin; thin mild steel sheet electrolytically coated with a layer of pure tin on both sides.

A derivative, iron chrome, has become an important, representing 30% of total tonnage.

Tin

The tin is made of steel, alloy of iron and other materials, and a layer of tin (Figure 2).

  1. The base steel

The chemical composition of the steel base also influences the mechanical properties of packaging and may play a role in resistance to corrosion.

  1. The tinning

Directed by electrolytic tinning can continuously depositing a precise amount of tin on each side of the metal which has been previously scoured and defatted. This deposit is then melted to obtain an alloy with the support and shiny feature. Finally, the surface receives an electrochemical passivation treatment to achieve a surface layer containing tin oxides, chromium oxides and chromium metal. Finally, he gets a very light oiling it easier to slip and protection before opening.

In practice, the rate of tin, expressed in g / m 2, are chosen depending on the type of box, the contents and terms of implementation. Standardization recommends the following nominal values: 1.0 - 2.0 to 2.8 - 5.6 - 8.4 and 11.2 g / m 2 per side. However, rates lower than 2.8 g / m 2 are not used for canned products.

Chrome iron

It is a material composed of steel and a layer of chromium, the addition operation of the layer is called "chrome."

Developed in Japan around 1965, this family of coatings has emerged in the U.S. and in Europe as the indispensable complement of tinplate.

The name of the international iron is chrome ECCS (ELECTROLITIC CHROMIUM COATED STEEL) but the common name TFS (TIN FREE STEEL) is still commonly used.

Aluminium

It is a material widely used in food processing, it presents the following characteristics:

  1. Lightness.
  2. Sealing against gases.
  3. Recyclable.
  4. Flexible.
  5. Stable.

However, this material has some drawbacks:

  1. Relatively expensive.
  2. Closure difficult.
  3. Limited marketing functions (limited forms).

The protective coating of metal packaging

Some metallic materials such as aluminum or iron are often chrome coating on both inner and outer. The essential function of the varnish is to minimize the interactions of metal packaging with products packaged and the external environment. Outside, the organic coatings simultaneously ensure the protection function and decoration.

The varnishes are products capable of forming an adherent film to the metal, continuous and inert physico chemical standpoint, that is to say that migration can occur during contact containment will not compromise the safety of foodstuff.

Their main constituents of varnish are:

  1. film-forming materials (organic polymers);
  2. solvents required in the manufacture and implementation of varnish but eliminated during drying;
  3. Possible pigments and various additives.

Unpigmented varnishes are transparent or colorless; pigments cloud the film and color, include for example titanium oxide coatings can be white, this polish is starting to become the essential component of inks for outdoor decoration the color and attractiveness that gives the package.

Plastics

Plastic packaging is a good deal of used packaging in the food industry. The practical aspect of the EMBA lage plastic plays a very important role in the consumer products of mass consumption. Products that have had their approval such as a spout for easy reuse and practical and are therefore offer another service to the consumer.

These packages offer an infinite variety of solutions, they adapt to the custom and endless content. Thanks to their lightness, their recoverability, whether by recycling or energy recovery, packaging after use to meet environmental requirements.

Plastic packaging is strong, it prevents loss of product, risk of damage to the food it protects. It has adapted to the packaging speed of the food industry and ways of distribution.

All the above requirements of food product packaging, whether technical, safety, health, compatibility containment, consumer convenience, information, marketing, explained that thanks to their diversity, both in terms of materials of modes processing, plastics are present in a number of increasingly wide applications.

Different materials most used are: PET, HDPE, LDPE, PS, PVC, PP.

Materials and their applications

The choice of materials

The primary rigid packaging, therefore in contact with food must meet a set of constraints requires that the material lends itself to the technique of transformation necessary to obtain the bottle of the tray or pot, but also provide the required properties:

  1. Shock resistance, cold (freezer) and temperature (eg sterilization, microwave);
  2. Attractiveness radius of stores (shape, color, appearance, transparency, power of seduction);
  3. Convenience for the consumer: opening / closing easy (screw cap, snap hinge cap, seal peelable lid), distributor of doses;
  4. Shelf life: packing barrier to water vapor, oxygen and odors. Used for modified atmosphere packaging;
  5. Consumer Safety: tamper-evident on the opening, sealing.

However the primary function of food packaging is undoubtedly ensure the protection of food against the risk of chemical and microbiological contamination during the outer shelf provided. All plastics offer this view, the barrier properties and safety that often prove satisfactory even in a monolayer packing (In the next paragraph, these polymers are called "structural materials") .

Where the food is inherently sensitive to oxygen or odors should be called to materials 'barrier'. These are then routinely used in multilayer packaging in combination with structural materials.

The materials 'barrier'

These materials have very low permeability to oxygen and carbon dioxide, but also to heavier molecules such as food flavorings. The current trend of increasing duration limit consumption encourages more use. However their other characteristics, including their price, do not allow their wide use.

  1. Ethylene vinyl alcohol copolymer (EVOH)

It is a material widely used in rigid food packaging because it lends itself well to the coextrusion of sheet or hollow body in combination with structural materials such as polyethylene, polypropylene or polystyrene. The crystalline character and polar EVOH, however, requires the use of binders that provide adhesion with the structural materials.

This copolymer has excellent impermeability to oxygen, carbon dioxide and aromas but provided to protect from the influence of moisture that brings down performance significantly. To overcome this drawback, it is often sandwiched in multilayer structures (Figure 3) based on polyolefins PE and PP insensitive to moisture.

This optimization of the structure can also be found by adjusting the rate of ethylene in the EVOH, which in practice varies from 29% to 44% by weight. The ease of implementation and lower humidity sensitivity increases with the rate of ethylene. In contrast, the barrier properties increase with vinyl alcohol content.

  • Polyvinylidene chloride (PVDC)

This family of materials "barriers" the most commonly used in flexible films. It is in fact composed of polyvinylidene chloride copolymers.

  • UV absorbers (Tinuvin 326)

Among the UV absorbers, Tinuvin 326 which is has been shown effective in delaying the absorption of UV radiation. This compound, which was approved by the FDA (Food and Drug Administration) as an additive for food packaging in April 1981, s' is proven effective against photooxidation of soybean oil (Pascal et al., 1995) and protects vitamin A against photooxidation (Ship et al. 1983; Fanelli et al., 1985).

Structural materials and their associations
  • Low density polyethylene (LDPE)

This material largely dominates the flexible packaging because it provides excellent impermeability to moisture and heat sealability at high speed. It can be used for liquid food products.

  • High Density Polyethylene (HDPE)

HDPE (Figure 4) made a remarkable breakthrough in two areas where the carton has dominant positions: Milk and fruit juices. Indeed, freedom of form, color and convenience of plastic bottles have renewed the marketing of these products.

Long life milk is packaged in multilayer bottles to avoid spoilage of milk by photooxidation.

Note that for fresh fruit juice, with a shelf life of several days in HDPE bottles translucent monolayer can be achieved through multilayer packaging made of HDPE-binding-barrier material-binder-HDPE, like the structure shown in Figure 3 (in this structure HDPE is the material structure within which we have built a barrier material to increase the "shelf life" of the product). Such a structure can increase the shelf life of juices up to 9 months.

Part of edible oils is packed in opaque HDPE bottles especially sunflower waxes whose presence may influence consumer behavior by giving them a turbid appearance unappreciated.

  • Polypropylene (PP)

It belongs to the family of polyolefins, essentially from propene. He enters mainly in the manufacture of packaging films packet of cigarettes, flowers, hosiery and dry foods (Figure 5).

This material offers several advantages:

  1. Good value for money;
  2. Adequate stiffness and transparency in food production;

The PP is used for packaging of mayonnaise and ketchup squeeze bottles, but to complete the transaction must incorporate an oxygen barrier such as EVOH in a multilayer structure of PP-binding type-EVOH-PP-binding .

Thermoforming of polypropylene has allowed this material to conquer other parts of the market such as desserts, fresh cheese, fruit, cookies in tins family ...

  • Compact polystyrene (PS)

Polystyrene (PS) (Figure 6): the polymer of styrene is mainly used in packaging of dairy products (yogurt, sour cream, dairy desserts) and vending cups. Polystyrene is the ideal material suitable for thermoforming a high rate, the PS still dominates in the packaging of fresh dairy products, like yogurts, dairy desserts, fromage frais. It is also the only material used in the technique known as "Form Fill Seal (FFS)" which is to follow up on the same production line, thermoforming, filling and sealing closure.

PS yoghurt pots manufactured by FFS are then sold in linear batch 4, 6 or 8 cans uncut. The consumer can easily separate the pots by folding.

For products sensitive to oxygen or long-term conservation should be implemented multilayer structures of PS / EVOH / PE. This is the case of meat or meat packaged in modified atmosphere and also fruit sauces.

  • Polyethylene terephthalate (PET)

This plastic has the polyester family, unlike PVC, a very low permeability to CO 2. It is used in the manufacture of soft drink bottles, and he is also involved in the manufacture of bottles of cosmetics.

Polyethylene terephthalate (PET) has become the material of choice for packaging edible oils as it offers better protection against oxygen and high resistance to shocks. Minimizing the

photooxidation alteration in blister packs can be ensured by the use of UV stabilizers or colorless components that absorb UV radiation (Dexter, 1984).

Such as polypropylene, PET (Figure 7) is experiencing strong growth in packaging and especially in the packaging of beverages and bottled waters.

Cellulosic materials in the service of food packaging

Types of cellulosic materials

Cellulosic materials (wood, paper, cardboard) are an important part in the packaging sector, especially for non-liquid food where employment up to 40% by the French committee of packing paper cardboard (1992).

Use of cellulosic materials

  1. The timber for packaging dry and fresh fruits (apples, mangoes, dates, raisins ...), it offers the advantage of easy handling and stacking.
  2. The glass bottle stoppers made of cork of cork oak.
  3. Cardboard and paper used for packing fruits and vegetables,

Conclusion

The choice of food packaging is extremely important in any food business. A choice that should be first subjected to an often tedious to determine all the endogenous and exogenous factors that may affect the quality of the food in question or to influence consumer choice.