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Food preservation and packaging

Introduction

Packaging has been with humans for thousands of years in one form or the other. Packaging dates back to when people first started moving from place to place.

Originally, skins, leaves, and bark were used for food transport.

Four thousand years ago, sealed pottery jars were used to protect against rodents, and glass making was an important industry in Egypt.

Tin-plating iron became possible in AD1200, and as steel replaced iron this method became useful

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One hundred years ago there was little use for packaging in the food industries.

Now, tremendous progress has been made in the development of diversified packaging materials and in the packaging equipment.

Over the last three decades, packaging has grown in volume and importance into one of the most significant areas of food production.

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Packaging performs five main functions

1- product containment

2- preservation and quality

3- presentation and convenience

4- protection during Distribution and Processing

5- provide storage history

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1-Product Containment

The first function of packaging is its capability of containment.

The primary purposes of packaging are containment and protection.

It is self-explanatory; liquids, semi liquids, and powders, as well as bulk solids, cannot be marketed without suitable containers.

Containment refers to holding goods in a form suitable for transport, whereas protection refers to safekeeping goods in a way that prevents significant quality deterioration.

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2-Preservation by Maintaining Quality

The second function of packaging is to control the local environmental conditions to enhance storage life and safety.

The main purpose of food packaging is to protect the product from surroundings and maintain the quality of the food throughout the products shelf life.

Product shelf life is controlled by three factors:

1-product characteristics,

2- properties,

3- storage and distribution conditions of individual package .

Reactions causing deterioration in foods include enzymatic, chemical, physical, and microbiological changes. Additional problems include insects, pests, and rodents.

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Nutritional Quality

Packaging affects the nutritional quality of foods. Examples include peroxidation of polyunsaturated fats and destructive oxidation of nutrients such as ascorbic acid,

Fatty acid peroxides are well established as causing health problems.

As antioxidative nutrients such as vitamins C and E are lost.

Carotenoid pigments can also be oxidized, leading to loss of color as well as loss of their beneficial effects in the body.

Lipid hydroperoxides can also result in the formation of aldehydes and other compounds with off-flavors. In addition to light barriers, use of UV absorber in the packaging material can decrease lipid oxidation.

Among all other functions of packaging, the protection of foodstuffs against light plays a key role particularly during storage, transport, and sales display.

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To achieve the best from packaging , it is important to know product characteristics, properties of individual package, storage, and distribution conditions.

Barrier properties include permeability of gases (such as O ,Co ,N , CH ), water vapor, aromas, and light. These are vital factors for maintaining the quality of foods.

packaging materials cannot be chosen solely on the basis of their barrier properties.

Barrier Properties

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Now various types of active substances can be incorporated into the packaging material to improve its functionality and give it new or extra functions.

Such Active packaging technologies and Antimicrobial Packaging and Edible Film are designed to extend the shelf life of foods, while maintaining their nutritional quality and safety.

Factors such as proccessability , mechanical properties and chemical resistance and interaction with product and Environmental factors, such as temperature, relative humidity, and light intensity must also be taken into account.

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3- Presentation and Convenience

Food labels are intended by law to provide the information that consumers need to be able to make the necessary decisions about those purchases of food.

It is important to display the product in an attractive manner to the potential buyer.

A cleverly designed and beautifully produced packaging can help sell a product, which is an essential ingredient of an effective marketing campaign . The packaging helps in distinguishing products on the shelf, which is a trait especially important when marketing low-fat or nutritional products.

For a package to be effective, it must present the product well and should do its own publicity.

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Changes in society, such as diminishing population pattern, increasing average age, smaller families, more leisure time, as well as improvements in the quality of life, standard of living, and general level of education, may also demand specific function of packaging.

Eating styles, such as ready-to-eat meals, snacks, and microwaveable ready meals, have been changed over the years, which need innovation in packaging.

Packaging should meet the future demand of meeting eating style of the society.

For children, the packaging might represent innovation or fun.

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4- Protection during Distribution and Processing

The fourth function is to protect the product during transit to the consumer.

Packaging is part of the distribution process necessary to deliver goods to the consumer and facilitate handling and transportation.

It also has affected international trade by making shipping of food products possible, allowing seasonal products to be more accessible out of season.

Packaging can handle better when there are challenges in food distribution chain, such as heat, humidity, or dew.

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It is important to be aware of the distribution challenges and designing of package to suit it.

In case of prepacked product, it should have the ability to stand the severity or type of process conditions , such as flexible packaging during canning, microwaveable foods, ovenable , and retortable foods.

Irradiated foods are usually prepacked prior to treatment by ionizing radiation.

Protective packaging is a term applied to packaging primarily designed to protect the goods, rather than for appearance or presentation.

5-Provide Storage History

Time-temperature indicator (TTI) is effective for predicting microbial concentrations and other parameters of food quality during shipping and storage.

It helps in ensuring proper handling and provides a gauge of product quality for sensitive products in which temperature control is imperative to efficacy and safety..

TTI could be used in chilled foods to identify the temperature abuse during storage and distribution.

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TTIs are tags that can be applied to individual packages or shipping cartons to visually indicate whether a product has been exposed to time and temperature conditions that adversely affect the product quality.

According to the response mechanisms, TTIs can be divided into three groups: (i) biological, (ii) chemical, and (iii) physical systems

There are two issues to be considered:

One is the economics .

The other issue is knowledge of the food product.

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Packaging categories

1- primary packaging

2- secondary packaging

3- transit packaging

wrapping used to bundle the boxes or crates

for transport and distribution.

Primary packaging surrounds the product

and features labelling.

ease of manual movement of products.

Transit packaged products are placed in shipping containers for long-distance transportation and distribution

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Selecting the right material

Material selection is based on:

technical properties (strength, flexibility, etc.)

fitness for purpose (moisture barrier, cushioning, etc.)

availability

manufacturing capability

cost

environmental impact

regulations

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Types of Packaging Materials

From skins, leaves, and bark, tremendous progress has been made in the development of diversified packaging materials and in the packaging equipment.

In general, packaging materials may be grouped into

1- rigid (wood, glass, metals, and hard plastics )

2-flexible structures. (Plastic film, foil, paper, and textiles )

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1- Plastics

Their foremost advantage is their wide diversity and extremely broad spectrum of properties.

Plastics are relatively cheap, light, easily processed and shaped, and easy to seal.

Two major drawbacks are their permeability to gases and vapors , and the possibility of their interacting with the product.

Other components in plastics are residual monomer and oligomers, additives such as heat and light stabilizers, antioxidants, plasticizers, and UV absorbers, as well as processing aids such as lubricants, slip agents , and antistatic agents.

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For package sterilization, the material of choice is polypropylene (PP), which is used as the outer and inner plies of the laminate with polyvinylidene chloride (PVDC) as the middle layer to provide an oxygen barrier.

Plastic Bags

Plastic Closures

Oven-Safe Containers

The three main plastics used are :

PP, PS, and CPET. PP is suitable for microwaves.

but now, PS low-density blends have been developed with heat deflection temperatures (HDTs) of 190C, which is suitable for microwaves.

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PlasticFood Interaction

Polymer materials are not absolute barriers.

Interactions occur between foods, packages, and polymer materials

In case of plastics, the major source of concern is the component migration.

Migration from plastics is mainly due to:

1- residual components and reactants from the manufacturing process

2- compounds formed during conversion into packaging materials and packages,

3- additives incorporated for functionality

4- adhesives used during conversion.

Other factors includes crystallinity of polymers, glassrubber transition, environmental conditions, and composition of packaged food.

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Toxicological implications of component migration from packages into foods are another serious problem.

Migration in plastics packaging refers to the transfer of compounds from the plastic to the food product.

This might be by leaching or diffusion.

Direct contact between plastic and a food product can result in components of the packaging being leached out into the product, changing the flavors of the food.

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The main components that have caused problems are: amides heat-degradation products from the polymer base, and ink components.

Migration may also occur from the food to the plastic, in some cases resulting in plasticizing of the package if the vapors are water or certain solvents. This can result in loss of mechanical strength.

The food may lose valuable volatiles, such as odors, carbon dioxide, water, or flavors.

Metals (Steel, Tin, Aluminum)

Steel, tin, and aluminum are used mainly for canned foods and beverages. The most common use of metals for packaging is in tin-coated steel and aluminum cans.

The principal advantages of metal cans are their strength providing mechanical protection, effective barrier properties, and resistance to high temperatures providing stability during processing.

it is an advantage for light-sensitive products.

disadvantage in that contents are: invisible, heavy mass, high cost, and tendency to interact with contents and environment (internal and external corrosion)

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The critical concepts of canning are to ensure that the product in the can is stable and that the seal provided by the metal is complete.

Aluminum is used increasingly for canning due to its lightness, low cost, corrosion resistance, availability, and recyclability.

Aluminum is also used extensively in many non canning applications such as foil packaging, caps, convenience food containers and lids, yogurt tub lids, kitchenware, and laminates.

Foil may be used for formed or semirigid containers.

Aluminum foil is difficult to use on modern fast packaging equipment because of creases, tearing, and marking effects

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The steel can provide almost perfect barrier protection and, due to its structural strength and ability to handle pressure, can be retorted (cooked under pressure) after sealing .

MetalFood Interaction:

Corrosion is the destructive attack on a metal through the chemical or electrochemical reaction with the environment. Since steel corrodes rapidly in the presence of acidic substances, the tin acts as a barrier.

Some cans are lacquered internally for high-acid products (pH < 3) or for products that change color in the presence of tin.

Foods that contain sulfur produce a blackening of the tin.

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The most important corrosion accelerators in foods include acidity, oxygen, nitrates, sulfur compounds, trimethylamines, anthocyanins, dihydroascorbic acid as well as severity of heat treatment and storage conditions.

Corrosion products in food cans are limited to three metals: tin, iron, and lead, which are liable to dissolve from the container. Of these only lead is toxic and cumulative in body tissues, hence a hazard.

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Glass

Advantages:

Glass containers used to be and still are considered a prestigious means of packaging, and serve for the most expensive wines, liqueurs, perfumes, and cosmetics.

It is highly inert, impermeable to gases and vapors, and amenable to the most diverse shaping. It is an excellent oxygen barrier and completely neutral in contact with foods

It has the advantage of transparency, but where required it can be given different desired colors.

It has complete as well as selective light protection properties.

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Disadvantages are :

fragility, heavy mass, and high energy requirement during

manufacturing.

The main uses of glass for packaging are in milk bottles, condiments, baby foods, instant coffee, and drinks.

Glass is not used for frozen products, or for ground or roasted coffee because of breakage costs and the difficulty of vacuum flushing.

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Timber, Cardboard, and Papers

Pulp products are widely used in food packaging in the form of different kinds of paper, paperboard, laminates, and corrugated board.

The main advantages of paper are its low cost, low mass, relatively high stiffness, and excellent printability;

the main disadvantage is its high sensitivity to moisture, reflected in close dependence on the relative humidity of the environment.

The basic raw material for papermaking is cellulose.

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Wood is commonly used in box construction, but the use of wood for individual packaging (such as cigars) has decreased since the advent of plastics. Examples of timber for packaging are cases, boxes, and casks for long-distance transport.

Cardboard

Timber

Choosing a carton for a specific job depends on the capacity of the carton to meet the requirements for that job.

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Environmental Issues

Recently, a new dimension of safety has arisen, the ecological dimension.

This means that packaging has not only to satisfy physical,chemical, and biological criteria using their life cycle as packaging, but once the original function has been fulfilled the packaging should decay without polluting the environment.

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Biodegradable material for packaging

Biodegradation is the process by which carbon-containing chemical compounds are decomposed in the presence of enzymes secreted

by living organisms.

There are three requirements for the fast degradation process viz. temperature, humidity and type of microbes.

Acceptable bioplastics are listed below

1- Cellulose

2- Starch

3- Poly-beta-hydroxyalkanoates (PHB)

4- Polylactide Acid (PLA) plastics:

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Application of nanocomposites

Research on application of nanocomposite (scale of 1e100 nm) materials nanomaterials) in packaging is exponentially increasing.

Nanocomposite materials are composed of nanoscale structure that enhances the macroscopic properties of food products.

The common nanocomposites used in the food packaging industry are:

(1) Polymer clay nanoclay increased stiffness, strength, nucleating agent in foams, smaller cell size, higher cell density, and flame retardant

(2) Silica nanocomposites of nanosilverhas excellent antibacterial properties

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Types of Packages

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Modified-Atmosphere Packaging

The modification of the atmosphere generally implies a reduction of O2 content or an increase of the CO2 concentration, but in some cases changing the level of carbon monoxide (CO),ethylene, ethanol, or other compounds in the atmosphere can also contribute to shelf-life extension.

After closing the package, the respiration of the product will cause a decrease in the oxygen content and an increase in the carbon dioxide content.

The course of the atmosphere modification is determined by three interacting processes: respiration of the commodity, gas diffusion through the commodity, and gas permeation through the film. Each of these processes is in turn strongly influenced by several commodity- and environment-generated factors.

Strict temperature control in the distribution chain would be a prerequisite for optimal use of MAP in practice.

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Controlled-Atmosphere Packaging

In CAP, the altered gas composition inside the package is monitored and maintained at a preset level by means of scrubbers and the inlet of gases. This method closely resembles the practices used in large controlled-atmosphere (CA) storage facilities where produce is stored essentially unpacked in bulk,except that CAP is used for storage or transport of smaller quantities of produce.

The ULO storage uses O2 levels close to the minimum level required for maintenance of plant tissues.

Using ULO storage at 1C2C with preset levels of 0.5%1% O2 and 2%3% CO2, for instance, Elstar apples can be stored for almost a whole year without unacceptable quality loss.

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Active Packaging

In some cases, a package cannot be designed in such a way that optimal conditions will be reached passively.

Active packaging can then provide a solution, by adding materials that absorb or release a specific compound in the gas phase.

Compounds that can be absorbed are carbon dioxide ,oxygen, water vapor, ethylene, or volatiles that influence taste and aroma.

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Vacuum Packaging

Vacuum packaging (VP) may be regarded as a special type of MAP, since part of the normal headspace is removed, leaving an altered initial atmosphere that is not controlled after packaging.

In this system, the initial gas composition is that of normal air, but because of the reduced partial gas pressure, the amount of O2 available at the start of storage is about one-third of the normal amount.

As with MAP, the lower O2 content stabilizes the postharvest product quality by slowing down the metabolism of the produce and the growth of spoilage microorganisms.

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Modified-Humidity Packaging

MAP, CAP, and VP all focus on changing the metabolic gases oxygen and carbon dioxide.

Modifiedhumidity packaging (MHP), however, is designed for products where dehydration causes the most important quality losses, and therefore focuses on controlling water vapor levels. When products such as leafy vegetables or bell peppers are not packed, quality losses can be observed very soon.

In most closed packages such as MAP, CAP, and VP, the RH is close to saturation due to the water exchange between the product and the headspace. This high humidity increases the probability of condensation and free water accumulating directly on the product, especially when the package is exposed to changing temperatures.

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MHP systems are designed to control not only dehydration but also condensation.

Control of the in-package RH may be pursued through the use of packaging materials with high water vapor permeabilities, by inclusion of sachets containing water absorbers like CaC12, sorbitol, or xylitol in the package or by use of packaging materials with suitable gas permeabilities onto which such desiccants are coated.

Aseptic packaging

Is considered the most appropriate way of packaging for pulsed electric fields (PEF) processed foods.

Smart packaging

A package can be made smart through its functional attributes that add benefits to the food and hence the consumers.

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Non-thermal processing

and

packaging

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1- do not utilize increased temperature to inactivate decomposing microorganisms and enzymes. This is the biggest advantage .

2-hurdle technology is the term often applied when foods are preserved by a combination of processes.

3- These methods produce far less volatile odour of plastics, additives, and printing solvent.

This is very beneficial to high-fat foods and frozen/refrigerated foods.

4-There is no general requirement for packaging materials for all non-thermal processes.

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High-pressure technology

involves different packaging considerations, based on :

whether a product is processed in-container or packaged after processing.

The packaging material must be able to withstand the operating pressures, have good sealing properties, and the ability to prevent quality deterioration during the application of pressure.

the package should be flexibl enough to transmit the pressure.

The presence of headspace must be kept as small as possible.

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Irradiation

technology

The packaging materials Should be chemically stable under the radiation dose to prevent polymer degradation and low molecular weight hydrocarbons and halogenated polymers formation which can migrate into foods.

Radiolysis products (RPs) formed upon irradiation of a polymer or adjuvant could migrate into food and affect odour, taste, and safety of the irradiated food.

does not generally affect all properties of a polymer to

the same degree.

Monofilms where not significantly changed by irradiation :

PE-HD, PE-LD, PS.

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UV and UV/ozone treatment

Due to poor penetrative properties, UV light is more or less limited to surface applications, but it shows promise as a post-packaging treatment.

UV-light, usually used for sterilization of packages used in aseptic processing, is often combined with ozone treatment.

Ozone mainly reacts with the surface of the polymers and causes modification of the surface properties of polymers.

both UV and ozone treatment, significantly increased the surface tension and hydrophilicity of polymers such as PE, PP and PET, and improved their adhesion properties

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The effect of ozone on the mechanical properties of plastic films depends on the polymer and the treatment conditions such as ozone concentration and temperature.

Oxygen permeability of linear low-density polyethylene (PE-LLD) treated with ozone.

UV treated PE-LD produced lower amounts of oxidation products compared to PET.

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Ultrasound

Is used in processing lines to detect the leaks in packages and control the microbiological quality of several foodstuffs.

Ultrasound treatment of sodium caseinate edible films greatly improved tensile strength and puncture resistance of these films while water vapour permeability, elongation at break and moisture content of the films were not affected by this treatment.

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- Handbook of Food Preservation

1-Mohammad Shafiur Rahman

2-Kata Galic , Mario Scetar and Mia Kurek, (2011 ).The benefits of processing and packaging . Trends in Food Science & Technology

References

3-Nitaigour P. Mahalik and Arun N. Nambiar,(2011) Trends in food

packaging and manufacturing systems and technology. Trends in Food Science & Technology

4-Sandhya ,Krishi Vigyan Kendra, Punjab ,(2011) . Modified atmosphere packaging of fresh produce: Current status and future needs. LWT - Food Science and Technology

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