SNS College of Technology,Coimbatore-35. (Autonomous) B.E/B.Tech- Internal Assessment -I Academic Year 2019-2020 (Odd) Seventh Semester A Agriculture Engineering 16AG412–Packaging Technology

PART-A 1 Food authenticity means food should match the description 2 Which of the following is an example of tertiary packaging? of breakfast cereals 3 is a chemically inert packaging material 4 identifies the product or brand 5 Symbol used for purity of agricultural goods is all the above PART-B 6 List the basic functions of packaging Containment, Protection, Preservation, Information about the product, Convenience, Presentation, Brand communication, Promotion (Selling), Economy, Environmental responsibility 7 List the parameters of a climatic condition that can cause damage to a food product? Give example High/low temperature, Moisture, Relative humidity, Light, Gases and vapour, Volatiles and odours, Liquid moisture, Low pressure, Dust 8 Mention the three levels of packaging Primary packaging Secondary packaging Tertiary packaging 9 What is stretch packaging? Stretch film is a material made up of film. When heat is applied, it shrinks tightly over whatever it is covering. Heat can be applied with a hand held heat gun (electric or gas) or the product and film can pass through a heat tunnel on a conveyor. 10 Draw the layers of

PART-C 11 a. Write the functions of cushioning materials in packaging ➢ is used to protect items during shipment. and during shipment and loading/unloading are controlled by cushioning to reduce the chance of product damage. ➢ Cushioning is usually inside a shipping such as a corrugated box. It is designed to absorb shock by crushing and deforming, and to dampen vibration, rather than transmitting the shock and vibration to the protected item. Depending on the specific situation, package cushioning is often between 50 and 75 millimeters (two to three inches) thick. ➢ Internal packaging materials are also used for functions other than cushioning, such as to immobilize the products in the box and lock them in place, or to fill a void. ▪ When designing packaging the choice of cushioning depends on many factors, including but not limited to: ▪ effective protection of product from shock and vibration ▪ resilience (whether it performs for multiple impacts) ▪ resistance to creep – cushion deformation under static load ▪ material costs ▪ labour costs and productivity ▪ effects of temperature,[1] humidity, and air pressure on cushioning ▪ cleanliness of cushioning (dust, insects, etc.) ▪ effect on size of external ▪ environmental and issues ▪ sensitivity of product to static electricity

Common types of cushioning

• Loose fill – Some cushion products are flowable and are packed loosely around the items in the box. The box is closed to tighten the pack. This includes expanded pieces (Foam peanuts), similar pieces made of starch-based , and common popcorn. The amount of loose fill material required and the transmitted shock levels vary with the specific type of material. • – Paper can be manually or mechanically wadded up and used as a cushioning material. Heavier grades of paper provide more weight-bearing ability than old newspapers. Creped cellulose wadding is also available. (Movers often wrap objects with several layers of or embossed pulp before putting them into .) • pads – Multi-layer or cut-and-folded shapes of corrugated board can be used as cushions. These structures are designed to crush and deform under shock stress and provide some degree of cushioning. composite honeycomb structures are also used for cushioning. • Foam structures – Several types of polymeric foams are used for cushioning. The most common are: Expanded Polystyrene (also Styrofoam), , , and . These can be molded engineered shapes or sheets which are cut and glued into cushion structures. Convoluted (or finger) foams sometimes used. Some degradable foams are also available. Foam-in-place is another method of using polyurethane foams. These fill the box, fully encapsulating the product to immobilize it. It is also used to form engineered structures. • – Pulp can be molded into shapes suitable for cushioning and for immobilizing products in a package. Molded pulp is made from recycled and is recyclable. • Inflated products – consists of sheets of with enclosed “bubbles” of air. These sheets can be layered or wrapped around items to be shipped. A variety of engineered inflatable air cushions are also available. Note that inflated air pillows used for void-fill are not suited for cushioning. • Other – Several other types of cushioning are available including suspension cushions, thermoformed end caps[7] [8] , and various types of shock mounts. Design for shock protection

• Drop test of cushioned package to measure the transmitted shock • Proper performance of cushioning is dependent on its proper design and use. It is often best to use a trained packaging engineer, reputable vendor, consultant, or independent laboratory. An engineer needs to know the severity of shock (drop height, etc.) to protect against. This can be based on an existing specification, published industry standards and publications, field studies, etc. • Knowledge of the product to be packaged is critical. Field experience may indicate the types of damage previously experienced. Laboratory analysis can help quantify the fragility of the item, often reported in g's. Engineering judgment can also be an excellent starting point. Sometimes a product can be made more rugged or can be supported to make it less susceptible to breakage. • The amount of shock transmitted by a particular cushioning material is largely dependent on the thickness of the cushion, the drop height, and the load-bearing area of the cushion (static loading). A cushion must deform under shock for it to function. If a product is on a large load-bearing area, the cushion may not deform and will not cushion the shock. If the load-bearing area is too small, the product may “bottom out” during a shock; the shock is not cushioned. Engineers use “cushion curves” to choose the best thickness and load- bearing area for a cushioning material. Often two to three inches (50 – 75 mm) of cushioning are needed to protect fragile items. • Cushion design requires care to prevent shock amplification caused by the cushioned shock pulse duration being close to the natural frequency of the cushioned item.

Design for vibration protection

The process for vibration protection (or isolation) involves similar considerations as that for shock. Cushions can be thought of as performing like springs. Depending on cushion thickness and load-bearing area and on the forcing vibration frequency, the cushion may

1) not have any influence on input vibration 2) amplify the input vibration at resonance, or 3) isolate the product from the vibration. Proper design is critical for cushion performance.

Evaluation of finished package

Verification and validation of prototype designs are required. The design of a package and its cushioning is often an iterative process involving several designs, evaluations, redesigns, etc. Several (ASTM {American Society for Testing and Materials}, ISTA {International Safe Transit Association Standards. International Safe Transit Association (ISTA)}, and others) published protocols are available to evaluate the performance of a proposed package. Field performance should be monitored for feedback into the design process.

CUSHIONING MATERIAL b. Enumerate shrink packaging Shrink wrapping , also shrink wrap or shrink film, is a material made up of polymer plastic film. When heat is applied, it shrinks tightly over whatever it is covering. Heat can be applied with a hand held heat gun (electric or gas) or the product and film can pass through a heat tunnel on a conveyor. Composition • The most commonly used shrink wrap is polyolefin. It is available in a variety of thicknesses, clarities, strengths and shrink ratios. • The two primary films can be either crosslinked, or non crosslinked. • Other shrink films include PVC and several other compositions. • Co-extrusions and are available for specific mechanical and barrier properties for shrink wrapping food. For example, five layers might be configuration as EP/EVA/co- /EVA/EP, where EP is ethylene-propylene and EVA is ethylene-vinyl acetate copolymer. Manufacture • A shrink film can be made to shrink in one direction (unidirectional or mono-directional) or in both directions (bidirectional). • Films are stretched when they are warm to orient the molecules from their initial random pattern. • Cooling the film sets the film's characteristics until it is reheated: this causes it to shrink back toward its initial dimensions. • Prior to orientation, the molecules of a sheet or are randomly intertwined like a bowl of spaghetti. • The molecules are coiled and twisted and have no particular alignment. • However when a draw force is imposed, the amorphous regions of the chains are straightened and aligned to the direction of orientation. • By applying proper cooling, the molecules will be frozen in this state until sufficient heat energy is applied to allow the chains to shrink back. • One can visualize this phenomenon by stretching a rubber band and dipping it into liquid nitrogen so as to freeze in the stretched state. • The band will remain in this state as long as it is kept at sufficiently cold temperatures. • However, when enough heat energy is applied, the rubber band will shrink back to its original relaxed state. • Orientation on a commercial scale can be achieved using either of two processes: a tenter frame or a bubble process. • Tenter frame technology is used to produce a variety of “heat-set” products, with biaxially oriented polypropylene (BOPP) being the most common (heat-setting is a process whereby a film is reheated in a constrained state such that the shrink properties are destroyed). • The second commercial process is the bubble process, sometimes referred to as the tubular process. • In this process, a primary tube is produced by either blowing or casting the tube onto an external or internal mandrel, respectively. • It is common to use water to help cool the primary tube at this point. • After the primary tube has been cooled, it is then reheated and inflated into a second bubble using air much like a balloon is blown. • Upon inflation, the tube is oriented in both directions simultaneously. • The family of shrink films has broadened over the years with many multilayer constructions being sold today. • Shrink film attributes include shrink, sealability, optics, toughness, and slip. • With regard to shrink properties, there are onset temperature, free shrink, shrink force, shrink temperature range, memory, and overall package appearance. Applications • Shrink wrap is applied over or around the intended item, often by automated equipment. • It is then heated by a heat gun or sent through a or oven for shrinking. • Shrink wrap can be supplied in several forms. • Flat roll stock can be wrapped around a product, often with heat sealing to tack the film together. • Center folded film is supplied on a roll with the plastic is folded in half: product is placed in the center portion, the remaining three edges are sealed to form a , and the package then heated which causes the bag to shrink and conform to the product placed in the bag. • Pre-formed shrink plastic bags are used with one end open: the product is placed in the bag, sealed, and sent for heat shrinking. • Shrink wrap is commonly used as an on many types of packaging, including , boxes, beverage cans and loads. • A variety of products may be enclosed in shrink wrap to stabilize the products, unitize them, keep them clean or add tamper resistance. • It can be the primary covering for some foods such as cheese, meats, vegetables and plants. • Heat-shrink tubing is used to seal electric wiring. • Shrink bands are applied over parts of packages for tamper resistance or . It can also combine two packages or parts. • Shrink wrap is also commonly used within more industrial applications using a heavier weight shrink film. • The principles remain the same with a heat shrinking process using a hand held heat gun. • The following shrink wrap applications are becoming more widely used and accepted: - Industrial shrink wrap containment of large plant equipment/components, - Building temporary shrink wrap structures for storage or other business operational uses, - Shrink wrapping of palletized freight 12 a. From the innovation perspective, explain any two latest advancements in field of packaging technology. is the process in which substances are broken down by the action of microorganisms. The term is often associated with ecology, , and plastic materials (due to their long lifespan). Nowadays, the complex nature of biodegradation is better understood. It involves several steps like: biodeteriration, biofragmentation, assimilation, and mineralisation.

Biodeterioration proceeds on the surface of the polymer where its mechanical, physical and chemical properties are changed. Generally, the term refers to the activity of microorganisms growing on a given material. Bacteria, protozoa, algae, fungi, and lichenaceae are organisms, which are involved in the biodeterioration.

They cause the changes on the surface of a material. While microbial species are developing on the polymer, the biodeterioration increases, facilitating the production of simple molecules. are the carbon and nitrogen sources and growth stimulators for microorganisms. Microbial species can secrete a kind of glue (made of polymers like polysaccharides and proteins) and adhere to polymer surfaces. This substance penetrates into porous structures and alters moisture amount and thermal transfers.

The microorganism’s growth in the material increases the size of pores and provokes cracks. As a result, the structure of the material is destabilized. The microbial species that are developing on the polymer surface also contribute to the chemical biodeteriration. Chemolithotrophic bacteria release inorganic compounds like ammonia, nitrites, hydrogen sulphide, thiosulphates, and elementary sulphur, whereas chemoorganotrophic microorganisms liberate organic acids as oxalic, citric, gluconic, glutaric, glyoxalic, oxaloacetic, and fumaric acids. These compounds can alter material surface.

Biofragmentation is an important phenomenon necessary for the following assimilation of the molecules. During this process a high molecular weight polymer is fragmented into a mixture of oligomers and/or . The energy needed for scissions may be of diverse origin as thermal, light, mechanical, chemical, and/or biological. The abiotic involvement was described previously. Microorganisms secrete specific enzymes or generate free radicals to cleave polymers. Oxidoreductases and hydrolases are mainly concerned in the biofragmentation process. Cellulases and amylases belong to hydrolases group and are synthesized by soil microorganisms. They hydrolyse renewable polymers like cellulose and starch. Starch in some commercial composites is co-extruded with (e.g. Mater-Bi®) to enhance the biodegradability. If low molecular weight molecules can be identified within degradation media, the polymer is considered as fragmented. A lot of analytical techniques, which are useful to separate oligomers with different molecular weights, like GPC, HPLC for liquid phase or GC for gaseous phase, are currently available.

Biodegradable Polymers for

Polyethylene and polypropylene, which are conventional polymers, last in the environment for many hundred years after disposal. Mainly, they are applied for production of plastic bags, which are disposed after one single use. Furthermore, food and other biological substances often stain packaging materials, which makes physical recycling of these materials impractical and generally undesirable. On the contrary, the science offers biodegradable polymers, capable of degrading after disposal in bioactive environments by the enzymatic action of microorganisms such as bacteria, fungi, and algae.

Polyhydroxylalkanoates are produced from renewable resources by bacterial fermentation of sugar and lipids. They are or elastomeric polymers, depending on the used in the synthesis. These materials, alone or in a blend with synthetic polymer or starch, give packaging films. The polyhydroxybutyrate (PHB) is the most common type of polyester, which is obtained in the polymerization of 3- hydroxybutyrate monomer, with properties similar to polypropylene although more stiffer and brittle. Scientists from China produced several PHA polymers from food wastes used as carbon source. The produced materials had various physical and mechanical properties, like flexibility, tensile strength, and melting viscosity. Such production of polyhydroxylalkanoates is rather inexpensive, but until now the project has not found commercial application.

Starch Based Polymers

Starch is an abundant, inexpensive, and annually renewable material available from potatoes as well as corn and other crops. It is composed of amylose, a mostly linear alpha-D-(1-4)-glucan and amylopectin, a branched alpha- D-(1-4)-glucan, which has alpha-D-(1-6) linkages at the branch point. Ratios of amylase and amylopectin vary with the starch source

Starch can be thermoplastic (TPS), which is obtained by technology similar to extrusion cooking. It has destructurized, noncrystalline form, produced by various heat application. From pure thermoplastic starch, traditional plastic goods can be obtained. However its sensitivity to humidity makes it unsuitable for most applications.

Starch-based biopolymers can be obtained by blending or mixing starch with synthetic polymers. The properties and morphology of these blends can be adjusted easily and efficiently. Full advantage of this phenomenon was taken by Novamount Company to produce Mater-Bi® material. It is mainly formed into films and sheets, which found application in agriculture, waste management, packaging, personal care & hygiene, accessories for animals.

Poly(Lactic Acid)

Poly(lactic acid) can be synthesized by biological and chemical methods. The first one is more environmentally friendly, due to its renewable character. It is based on starch and other polysaccharides fermentation. It can be produced from corn, sugar beet, sugar cane, potatoes, and other biomasses.The second one was developed by industrial sector.

Lactic acid (2-hydroxy propanoic acid) contains an asymmetric carbon in its structure, which gives two optically active configurations. D- and L-enantiomers can be produced by bacteria and the amount of bot is adjustable, but some bacteria can produce only one isomer, whereas the chemical process gives the racemic mixture of both D- and L-enantiomers.

Poly(lactic acid) is totally biodegradable when composted at 333 K and above. The first step of the degradation is proceeding by hydrolysis to water-soluble compounds and lactic acid. Then microorganisms are able to metabolize these products into carbon dioxide, water and Biomass.

The biodegradation mechanisms of PLA are influenced by numerous factors, including the structure and hydrolysis media. The diffusion coefficients of the soluble oligomers depend mainly on molar mass, degree of swelling of the matrix, macromolecular conformation, rigidity, chemical structure, molecular weight distribution, impurity/monomer residue, stereochemistry, chain mobility, and crystallinity. The amorphous domain is more susceptible to biodegradation process.

Various route of PLA synthesis

Lifecycle of poly(lactic acid) b. How do you differentiate between two-piece and three piece metal cans THREE PIECE WELDED CANS

• Three-piece welded food cans are only constructed from steel, as aluminium is not suitable for welding by this particular process. • Coils of steel, after delivery from the steel maker, are cut into sheets approximately 1m2. • The cut sheets are then coated, and printed if necessary, to protect and decorate the surfaces. • Areas where the weld will be made on the can body are left without or print to ensure the weld is always sound. • The and inks are normally dried by passing the sheets through a thermally heated oven where the temperature is in the range 150–205°C. • Alternatively, for some non-food contact uses, ultraviolet (UV)-sensitive materials may be applied. • These are cured instantaneously by passing the wet coating/ink under a UV lamp. • The sheets are next slit into small individual blanks, one for each can body, each blank being rolled into a cylinder with the two longitudinal edges overlapping by approximately 0.4mm. • The two edges are welded by squeezing them together whilst passing an alternating electric current across the two thicknesses of metal. • This heats up and softens the metal sufficiently for a sound joint to be made. • If the can is internally coated with lacquer it is generally necessary to apply a repair side stripe lacquer coat to the inside of the weld to ensure coating continuity over the whole can. • For food cans, the can body now passes through a flanging machine where the top and bottom of the can body are flanged outward to accept the can ends. • For drink cans, the top and bottom edges of the can body are necked-in to reduce the diameter prior to the creation of the flanges. • This permits ends to be fitted which are smaller in diameter than that of the can body, reducing the cost of the end and the space taken up by the seamed can. • For both food and drink cans, one end is then mechanically seamed-on to the bottom of the can body. This end is commonly referred to as the maker’s end (ME). • Where easy-open ends are fitted to three-piece cans, it is common practice for this end to be fitted at this point, leaving the plain end (non-easy-open) to be fitted after filling. This practice allows the seamed easy-open end to pass through the finished can testing process. • The end applied by the packer/ after can filling is commonly referred to as the canner’s end (CE). • At this stage, tall food cans (height-to-diameter ratio more than 1.0) pass through a beading machine where the body wall has circumferential beads formed into it. • The beads provide additional hoop strength to prevent implosion of the can during subsequent heat process cycles. • All cans finally pass through an air pressure tester, which automatically rejects any cans with pinholes or fractures. This completes the manufacture of empty three-piece food and drink cans.

DWI Two-piece drawn and wall ironed (DWI) cans

• The DWI cans are constructed from uncoated tinplate or aluminium. • However, DWI cans for processed food are only made from tinplate as thin wall aluminium cans do not have sufficient strength to withstand the heat process cycles. • For this process, the coiled metal, as it is unwound, is covered with a thin film of water- soluble synthetic lubricant before being fed continuously into a cupping press. • This machine blanks and draws multiple shallow cups for each stroke like Drawn cans. • The cups are then fed to parallel body-making machines which convert the cups into tall cans. • This is the drawing and ironing process where the cups are first redrawn to the final can diameter and then rammed through a series of rings with tungsten carbide internal surfaces which thin (iron) the can walls whilst at the same time increasing the can height. • During this process the can body is flooded with the same type of lubricant used in the cupping operation. • In addition to assisting the ironing process, the lubricant cools the can body and flushes away any metallic debris. • No heat is applied to the can during this process – any heat generated being from the cold working of the metal as it is thinned. • After the forming of the can body the uneven top edge of the can is trimmed to leave a clean edge and a can of the correct overall height. • Trimmed can bodies are passed through chemical washers and then dried. This process removes all traces of lubricant and prepares the metal surfaces for internal and external coating and ultimately external decoration (drink cans only). • Cans receive a paper label and an external coating is applied by passing them under a series of waterfalls of clear lacquer which protects the surface against corrosion. • The lacquer is dried by passing the cans through a heated oven. • Following this can body now passes through a flanging machine where the top of the can is flanged outwards to accept the can end, which will be fitted after the can is filled with product. • The flanged can is next passed through a beading machine which forms circumferential beads in the can wall, to give added strength to the can. • After all the mechanical forming operations have been completed, every can is tested by passing through a light tester which automatically rejects any cans with pinholes or fractures. • The inside of each can is then coated with lacquer using an airless spray system. • The special lacquer is applied to protect the can itself from corrosion and prevent its contents from interacting with the metal. • This lacquer is finally dried in a thermal oven at a temperature of about 210°C.

DRD CANS Two-piece single drawn and multiple drawn (DRD) cans

• Pre-coated, laminated and printed tinplate or TFS is fed in sheet or coil form in a reciprocating press that may have single or multiple tools. • At each tool station the press cycle cuts a circular disc (blank) from the metal and whilst in the same station draws this in to a shallow can (cup). • During the drawing process the metal is reformed from flat metal into a three-dimensional can without changing the metal thickness at any point. • After this single draw, the can may be already at its finished dimension. • However, by passing this cup through a similar process with different tooling, it may be re-drawn into a can of smaller diameter and greater height to make a draw–redraw can (DRD). • This process may be repeated once more to achieve the maximum height can. • At each of these steps, the can base and wall thickness remain effectively unchanged from that of the original flat metal. • Following this body-forming operation, necking, flanging and beading operations follow according to the end use and height-to-diameter ratio of the can (as for three-piece welded cans). • For all two-piece cans pinhole and crack detection on finished cans is carried out in a light-testing machine. This measures the amount of light passing across the can wall using high levels of external illumination. • One advantage of two-piece cans is that there is only one can end instead of two, meaning that one major critical control hazard point is eliminated. • The single drawing process is also used to make aluminium- or steel-tapered shallow trays for eventual heat-sealing with coated metal foil. • The container bodies are constructed from metal laminated with organic film. • The single drawing processes are also used for the manufacture of folded aluminium baking trays and take away . • In this process the aluminium is allowed to fold, as the metal is converted from a flat sheet into a shaped container.

13 a. List and explain the intrinsic factor that affects the quality of foods Intrinsic factors - properties resulting from the make-up of the final product o water activity (aw) (available water) o pH/total acidity; type of acid o natural microflora and surviving microbiological counts in final product o availablility of oxygen o redox potential (Eh) o natural biochemistry/chemistry of the product o added preservatives (e.g. salt, spices, antioxidants) o product formulation packaging interactions (e.g. tin pickup, migration) Chemical/Biochemical Processes Oxidation • A number of chemical components of food react with oxygen affecting the colour, flavour, nutritional status and occasionally the physical characteristics of foods. • In some cases, the effects are deleterious and limit , in others they are essential to achieve the desired product characteristics. • Packaging is used to both exclude, control or contain oxygen at the level most suited for a particular product. • Foods differ in their avidity for oxygen, i.e. the amount that they take up, and their sensitivity to oxygen, i.e. the amount that results in quality changes. • Foods containing a high percentage of fats, particularly unsaturated fats, are susceptible to oxidative rancidity and changes in flavour. • Saturated fatty acids oxidise slowly compared with unsaturated fatty acids. Antioxidants that occur naturally or are added, either slow the rate of, or increase the lag time to, the onset of rancidity. • Three different chemical routes can initiate the oxidation of fatty acids: the formation of free radicals in the presence of metal ion catalysts such as iron, or heat, or light – termed the classical free radical route; photooxidation in which photo-sensitisers such as chlorophyll or myoglobin affect the energetic state of oxygen; or an enzymic route catalysed by lipoxygenase. • Once oxygen has been introduced into the unsaturated fatty acids to form hydroperoxides by any of these routes, the subsequent breakdown of these colourless, odourless intermediates, proceeds along similar routes regardless of how oxidation was initiated. • It is the breakdown products of the hydroperoxides – the aldehydes, alcohols and ketones that are responsible for the characteristic stale, rancid and cardboard odours associated with lipid oxidation. • Lowering the storage temperature does not stop oxidative rancidity because both the first and second steps in the reaction have low activation energies. • Reduction of the concentration of oxygen (both dissolved and in the headspace) to below 1%, removal of factors that initiate oxidation and the use of antioxidants are strategies employed to extend shelf life where rancidity is a shelf life limiting factor. • In snack products and particularly nuts the onset of rancidity is the shelf life limiting factor. Such sensitive products are often packed gas flushed to remove oxygen and packed with 100% nitrogen to protect against oxidation and provide a cushion to protect against physical damage. Enzyme activity • Fruits and vegetables are living commodities and their rate of respiration affects shelf life – generally the greater the rate of respiration, the shorter the shelf life. • Respiration is the metabolic process whereby sugars and oxygen are converted to more usable sources of energy for living cells. • Highly organised and controlled biochemical pathways promote this metabolic process. • Depletion and exhaustion of reserves used for respiration leads to metabolic collapse and an appearance associated with senescence. • Ethylene (C2H4) is a plant growth regulator that accelerates senescence and the ripening process. It is a colourless gas with a sweet ether-like odour. • All plants produce ethylene to differing degrees and some parts of plants produce more than others. • The effect of ethylene is commodity dependent but also dependent on temperature, exposure time and concentration. • As ethylene induces senescence it has a significant impact on quality loss Microbiological processes • Under suitable conditions, most microorganisms will grow or multiply. • During growth in foods, microorganisms will consume nutrients from the food and produce metabolic by-products such as gases or acids. • They may release extra-cellular enzymes (e.g. amylases, lipases, proteases) that affect the texture, flavour, odour and appearance of the product. • Some of these enzymes will continue to exist after the death of the microorganisms that produced them, continuing to cause product spoilage. • The key to achieving the desired shelf life of a product is to understand which microorganisms are likely to be the ones that will give rise to product spoilage, and what conditions can be used to either kill or reduce the rate of growth and multiplication. • Using knowledge of the initial levels of microorganisms and the conditions that destroy them or reduce their growth rate, food products are developed and designed by use of the best combination of intrinsic and extrinsic factors. Insect damage • Infestation of foods with insects can be extremely unpleasant for the consumer because it is often not detected until the opening of the product. • Insect infestation can occur at any point after manufacture, but is most likely during extended storage periods or during shipment. • Although the problem may not be the fault of the food manufacturer, loss of materials can be expensive and legal cases can severely damage the reputation of brands. Package pests are classified in two groups – penetrators and invaders. • Penetrators are capable of boring through one or more layers of flexible packaging materials. It is possible to reduce infestation with penetrators by preventing the escape of odours from the package through the use of barrier materials. • Invaders are more common and enter packages through existing openings, usually created from poor seals, openings made by other insects or mechanical damage. It is therefore important that seals are not vulnerable to attack from insects. • The corners of square packages can also be potential points of entry for insects. Moisture changes • Moisture changes leading to loss or gain of moisture is a significant physical cause of the loss of shelf life of foods. • Hygroscopic foods require protection from moisture take up which in dry products such as breakfast cereals and biscuits causes loss of texture, particularly crispness. • For breakfast cereals the inner liner provides most protection to the food. Its main purpose is to protect from moisture transfer so as to preserve the product characteristics. • The most effective type of liner will be determined during shelf life testing or by combining information from break point testing (holding at increasing humidities) and knowledge about the characteristics of the moisture permeability of the packaging material. • Protection or prevention of moisture loss is best achieved by maintaining the correct temperature and humidity in storage. In chilled and frozen foods, water loss (desiccation, dehydration or evaporation) can result in quality loss. • Severe dehydration in frozen foods leads to freezer burn – the formation of greyish zones at the surface due to cavities forming in the surface layer of the food. • Freezer burn causes the lean surfaces of meat to become rancid, discoloured and physically changed. Packaging in low water vapour permeability materials protects against water loss during storage and distribution. Barrier to odour pick-up • Dairy products, eggs and fresh meat are highly susceptible to picking up strong odours. • Chocolate products have a high fat content and sometimes bland flavour. Unacceptable flavour pick-up can result if they are inadequately wrapped and stored next to strong smelling chemicals, such as cleaning fluids, or in shops close to strongly flavoured sweets, such as poorly wrapped mints. • Packaging reduces the problem but most plastic materials allow quite a significant volatile penetration – the plastic materials used for vacuum packs and MAP have low permeability, and this reduces, but does not prevent, the uptake of foreign odours i.e. taints. Flavour scalping • If a chemical compound present in the food has a high affinity for the packaging material, it will tend to be absorbed into or adsorbed onto the packaging until equilibrium concentrations have been established in food and packaging. This loss of food constituents to packaging is known as scalping. • Scalping does not result in a direct risk to the safety of the food, or in the introduction of unpleasant odours or flavour. • However, the loss of volatile compounds which contribute to a food’s characteristic flavour affect sensory quality. • It is common for unpleasant flavours naturally present in a food to be masked by other flavours, the high notes. If the high notes are scalped by the packaging material, the product is either bland or unpleasant flavours are more perceptible. • The degree of scalping is dependent partly on the nature of the polymer and partly on the size, polarity and solubility properties of the aroma compound. • Where particular food-packaging combinations are susceptible to scalping, introducing an effective barrier layer may reduce the problem. • Such systems must be carefully designed and tested to high levels of sensitivity to ensure that permeation through the barrier is minimized Migration from packaging to foods • The direct contact between food and packaging materials provides the potential for migration. • Additive migration describes the physico-chemical migration of molecular species and ions from the packaging into food. • Such interactions can be used to the advantage of the manufacturer and consumer in active and intelligent packaging, but they also have the potential to reduce the safety and quality of the product, thereby limiting product shelf life. • Paper and board has been used to package food products for many years. Their composition is generally less complex than , presenting less scope for migration. However, a number of taint problems in foods have been attributed to paper and board packaging. • Health concerns have been raised over the use of recycled paper and board for food contact because of the possible migration of diisopropylnaphthalenes (DIPNs). These constituents, usually present in a number of isomeric forms, are commonly used in the preparation of special , such as carbonless and thermal copy paper. Research has shown that DIPNs are not eliminated during the recycling of paper and have the potential to migrate into dry foods, such as husked rice, wheat semolina pasta, egg pasta and cornflour. • Migration from can lacquers into canned foods has been another area of concern over recent years. The migrants considered to pose the greatest health concern are the monomers bisphenol-A and bisphenol-F, and their diglycidylethers, known as BADGE and BFDGE, respectively. A study into the mechanisms involved in the migration of bisphenol-A from cans into drinks found that it was necessary to heat the can to a temperature above the glass transition temperature of the epoxy resin (105°C) in order for the compound to be mobilized. • The popularisation of polymeric packaging materials has resulted in increased concerns over the migration of undesirable components into foods. These concerns are generally focused on the levels of residual monomers and plastics additives, such as plasticisers and solvents, present in polymers intended for direct or close contact with food. It is therefore important that the formulation of plastic packaging materials is designed so that the polymerization process is as complete as possible. b. Write a detailed note on retort pouch

Introduction

The retort pouch is a rectangular, flexible, laminated plastic, four-side hermetically sealed pouch in which food is thermally processed. It is a lightweight, high-quality, durable, convenient and shelf stable packs. Foods packed and processed in retort pouches are in successful commercial use for a wide variety of foodstuffs in several countries, particularly Japan. The materials from which retort pouches are made are either aluminum foil bearing/plastic laminates or foil-free plastic laminate films. Retortable pouches can be either preformed or in-line formed using form/fill/seal equipment. Common pouch structures are PET/nylon/foil/PP and PET/nylon/EVOH or PVDC/PP. Retortable pouches are used by hotels, restaurants, and other institutions.

Retortable pouches must be inert, heat sealable, dimensionally stable and heat resistant to at least 121°C for typical process times. They should have low oxygen and water vapor permeability, be physically strong and have good ageing properties. Retail consumer products such as tuna, salmon, chicken patties, chipped beef, chili, and ground beef in retortable pouches have become available. Pouches are reverse printed in a wide range of graphics on the PET film before , so that the print cannot come into contact with the food. All laminates are required to meet very stringent requirements to ensure no undesirable substances can be extracted into the packaged food.

Manufacturing of pouches

Pouches can either be formed from reels of laminated material either on in-line form/fill/seal machines in the packer’s plant or they may be obtained as preformed individual pouches sealed on three sides, cut and notched. Forming consists of folding the laminate material in the middle, polyester (or PA) side out, heat sealing the bottom and side seals and cutting to present a completed pouch. Alternatively two webs can be joined, heat seal surfaces face to face, sealed, cut and separated. Hot bar sealing is the most common practice. Notches are made in the side seal at the top or bottom to facilitate opening by the consumer. Modern pouches have cut rounded corners which reduce the possibility of perforation caused by pouch to pouch contact. Rounded corner seals can also be incorporated.

The four-seal flat shape and thin cross section of the pouch is designed to take advantage of rapid heat penetration during sterilization and on reheating, prior to consumption, saving energy and providing convenience. The flat shape also enables ease of heat sealing and promotes high seal integrity. Fin seal design and certain gusset features permit the design of upright standing pouches although they create multiple seal junctions with increased possibility of seal defects. Several of these upstanding pouches are, however, available commercially. A wide range is possible in the size and capacity of pouches.

Filling and sealing

The premade pouches are filled vertically in-line. Vertical form/fill/seal machines can be used for liquid products. Another method employs a web of pouch material which is formed on a horizontal bed into several adjacent cavities. The cavities are filled whilst the seal areas are shielded. This method is especially useful for filling placeable products. Thereafter the filled cavities are simultaneously sealed from the top using a second web fed from the reel. The essential requirements for filling are:

• Pouch should be cleaned, fully opened to the filling station, solids are filled first followed by the liquid food at a second station • Matching fill-nozzle design and filler proportioning to the product • Non-drip nozzles are used for filling • Shielding of the sealing surfaces • Bottom to top filling • Specification and control of weight consistent with the maximum pouch thickness requirement • Product consistency in formulation, temperature and viscosity • Deaeration prior to filling.

Sealing machines like fillers are constantly being refined and speed has improved from 30 to 60 pouches per minute to the current production rate of 120–150 pouches per minute. Sealers incorporate either one of two common satisfactory sealing methods namely hot bar and impulse sealing. Both methods create a fused seal whilst the pouch material is clamped between opposing jaws, thereby welding the opposing seal surfaces by applying heat and pressure. Exact pouch-sealing conditions depend on the materials and machinery used.

Quality assurance

A successful pouch packaging quality system requires:

• Selection and continued monitoring of the most suitable laminate materials. • Regular testing of formed pouches for seal strength, product resistance and freedom from taint. • Careful selection, maintenance and control of filling, sealing, processing and handling machinery. • Specifications for the control of product formulation, preparation (viscosity, aeration, fill temperature etc.) and filling (ingoing mass and absence of seal contamination). • Post sealing inspection and testing of seals to confirm fusion, absence of defects and contamination. • Control of critical parameters influencing processing lethality such as maximum pouch thickness and residual air content. • Standardized retorting procedures applying only recommended process times and temperatures confirmed to achieve adequate lethality. • Regular inspection and testing of retort equipment and controls to ensure uniform heat distribution. • Visual inspection of all pouches to check sealing after processing. • Handling only of dry pouches and packing into collective or individual outer packaging specially tested to provide adequate, subsequent, abuse resistance. • It should be routine that all stocks are held 10–14 days prior to distribution and these should be free of blown spoilage on dispatch. • Careful staff selection and training at all levels.

Shelf life

Whilst shelf life is determined by many factors such as storage temperature and the barrier properties of the particular film used, in general, satisfactory shelf stability in excess of two years is easily obtained for a wide range of products in foil bearing pouches. US military rations tested over two years at 20°C showed no significant change in product quality ratings. Some products have been successfully stored for as long as seven years and found to be safe and edible.

Foil-free laminates will demonstrate shelf stability commensurate with oxygen permeability of the particular laminate used and the sensitivity of the product. Commercial experience confirms, however, that product stability from four weeks to six months is obtainable. Nitrogen flushing of the outer container has been successful in extending the shelf life of product in foil-free pouches. .

Layers of retort pouch