Food Packaging Technology PDF

Food Packaging Technology Mr. Harsh Sharma Food Packaging Technology Author Mr. Harsh Sharma AAU, Anand  Index Lesson Page No Module- 1 Factors affecting shelf of food material...

Food Packaging Technology Mr. Harsh Sharma Food Packaging Technology Author Mr. Harsh Sharma AAU, Anand  Index Lesson Page No Module- 1 Factors affecting shelf of food material during storage, spoilage mechanism during storage Lesson- 1. Factors affecting shelf life of food 5-9 Lesson- 2. Spoilage mechanism during storage 10-13 Module- 2 Definition, requirement, importance and scope of packaging of foods, types and classification of packaging system, advantage of modern packaging system Lesson- 3 Functions of food packaging 14-17 Lesson- 4 Packaging systems 18-22 Lesson- 5 Modern Packaging System 23-26 Module- 3 Different types of packaging materials used Lesson- 6 Paper/Paperboard 27-31 Lesson- 7 Glass 32-34 Lesson- 8 Plastic 35-38 Lesson- 9 Metal 39-42 Lesson- 10 Other packaging materials 43-46 Module- 4 Different forms of packaging, metal container, glass container,plastic container,flexible films,shrink packaging,vacuum & gas packaging Lesson- 11 Metal Containers 47-50 Lesson- 12 Glass Containers 51-54 Lesson- 13 Plastic Containers 55-61 Lesson- 14 Retort Pouch 62-64 Lesson- 15 Vacuum, Gas and Shrink packaging 65-70 Module- 5 Packaging requirement & their selection for the raw & processed foods Lesson- 16 Role of Ideal packaging materials 71-75 Lesson- 17 Selection criteria of packaging material for raw foods 76-78 Lesson- 18 Selection criteria of packaging material for processed 79-83 foods Module- 6 Advantages and disadvantages of these packaging materials, effects of these materials on packed commodities Lesson- 19 Advantages of different packaging materials 84-87 Lesson- 20 Disadvantages of packaging materials 88-90 Lesson- 21 Effect of packaging materials on food commodities 91-94 Module- 7 Package testing Lesson- 22 Determination of parameters of different packaging 95-97 materials Lesson- 23 Identification of different packaging materials 98-106 Module- 8 Printing, labelling and lamination Lesson- 24 Printing 107-110 Lesson- 25 Labelling and lamination 111-113 Module- 9 Basics of Economics Lesson- 26 Basics of Economics 114-116 Lesson- 27 Economics of plastic packaging 117-120 Module- 10 Performance evaluation of different methods of packaging food products, their merits and demerits, scope of improvements Lesson- 28 Protective functions of food packaging 121-124 Lesson- 29 Performance evaluation of packaging on meat products 125-127 and dairy products Lesson- 30 Performance evaluation of packaging on fruits and 128-130 vegetables and other products Module- 11 Disposal and recycle of packaging waste Lesson- 31 Recycling of packaging 131-133 Lesson- 32 Recycling packaging materials 134-137 Food Packaging Technology Module- 1 Factors affecting shelf of food material during storage, spoilage mechanism during storage Lesson- 1. Factors affecting shelf life of food 1.1 Introduction Packaging is an essential part of processing and distributing foods. Whereas preservation is the major role of packaging, there are several other functions for packaging, each of which must be understood by the food manufacturer. Packaging must protect against a variety of assaults including microorganisms, insects and rodents. Environmental factors such as oxygen and water vapor will spoil foods if they are allowed to enter packages freely. Packaging can become a shelf life limiting factor in its own right. For example, this may be as a result of migration of tainting compounds from the packaging into the food or the migration of food components into the packaging. Different groups within the food chain, i.e. consumers, retailers, distributors, manufacturers and growers, proffer subtly different perspectives of shelf life, reflecting the aspect of greatest importance and significance to them. For consumers, it is imperative that products are safe and the quality meets their expectations. Consumers will often actively seek the product on the shelf with the longest remaining shelf life as this is considered to be indicative of freshness. 1.2 Shelf life The quality of most foods and beverages decreases with storage or holding time. The shelf life of a product is best determined as a part of the product development cycle. The Institute of Food Technologists (IFT) in the United States has defined shelf life as ―the period between the manufacture and the retail purchase of a food produ-ct, during which time the product is in a state of satisfactory quality in terms of nutritional value, taste, texture and appearance‖. The Institute of Food Science and Technology (IFST) in the United Kingdom has defined shelf life as ―the period of time during which the food product will remain safe; be certain to retain desired sensory, chemical, physical, microbiological and functional characteristics; and comply with any label declaration of nutritional data when stored under the recommended conditions‖. The date of minimum durability is defined as the date until which the food retains its specific properties when properly stored. It must be indicated by the words ―Best before‖ followed by the date (or a reference to where the date is given on the labeling). Depending on how long the food can keep, the date can be expressed by the day and the month, the month and the year, or the year alone. 1.3 Factors affecting shelf life 5 www.Agrimoon.Com Food Packaging Technology 1.3.1 Product characteristics Product characteristics including formulation and processing parameters i.e. intrinsic factors. Intrinsic factors are the properties resulting from the make-up of the final product and include the following:  Water activity (aw)  PH/total acidity  Natural micro flora and surviving microbiological counts in final product  Availability of oxygen  Reduction potential (Eh)  Natural biochemistry/chemistry of the product  Added preservatives (e.g. salt, spices, antioxidants)  Product formulation 1.3.2 Environmental factors Environment to which the product is exposed during distribution and storage i.e. extrinsic factors. Extrinsic factors are a result of the environment that the product encounters during life and include the following: 1.3.2.1 Temperature Temperature is a key factor in determining the rates of deteriorative reactions, and in certain situations the packaging material can affect the temperature of the food. For packages that are stored in refrigerated display cabinets, most of the cooling takes place by conduction and convection. Simultaneously, there is a heat input by radiation from the fluorescent lamps used for lighting. Under these conditions, aluminum foil offers real advantages because of its high reflectivity and high conductivity. 1.3.2.2 Relative humidity The RH of the ambient environment is important and can influence the water activity (aw) of the food unless the package provides an excellent barrier to water vapor. Many flexible plastic packaging materials provide good moisture barriers, but none is completely impermeable. 1.3.2.3 Gas atmosphere The presence and concentration of gases in the environment surrounding the food have a considerable influence on the growth of microorganisms, and the atmosphere inside the package is often modified. The simplest way of modifying the atmosphere is vacuum packaging, that is, removal of air (and thus O2) from a package prior to sealing; it can have a beneficial effect by preventing the growth of aerobic microorganisms. Flushing the inside of the package with a gas such as CO2 or N2 before sealing is the basis of modified atmosphere packaging (MAP). For example, increased concentrations of gases such as CO2 are used to retard microbial growth and thus extend the shelf life of foods. MAP is increasing in importance, especially with the packaging of fresh fruits and vegetables, fresh foods, and bakery products. Atmospheric O2 generally has a detrimental effect on the nutritive quality of foods, and it is therefore desirable to maintain many types of foods at a low O 2 tension, or at least 6 www.Agrimoon.Com Food Packaging Technology prevent a continuous supply of O2 into the package. Lipid oxidation results in the formation of hydroperoxides, peroxides, and epoxides, which will, in turn, oxidize or otherwise react with carotenoids, tocopherols, and ascorbic acid to cause loss of vitamin activity. With the exception of respiring fruits and vegetables and some fresh foods, changes in the gas atmosphere of packaged foods depend largely on the nature of the package. Adequately sealed metal and glass containers effectively prevent the interchange of gases between the food and the atmosphere. With flexible packaging, however, the diffusion of gases depends not only on the effectiveness of the closure but also on the permeability of the packaging material, which depends primarily on the physicochemical structure of the barrier. 1.3.2.4 Light Many deteriorative changes in the nutritional quality of foods are initiated or accelerated by light. Light is, essentially, an electromagnetic vibration in the wavelength range between 4000 and 7000 A, the wavelength of ultraviolet (UV) light ranges between 2000 and 4000 A. The catalytic effects of light are most pronounced in the lower wavelengths of the visible spectrum and in the UV spectrum. The intensity of light and the length of exposure are significant factors in the production of discoloration and flavor defects in packaged foods. There have been many studies demonstrating the effect of packaging materials with different light-screening properties on the rates of deteriorative reactions in foods. Among the most commonly studied foods has been fluid milk, the extent of off-flavor development being related to the exposure interval, strength of light, and amount of milk surface exposed. 1.3.3 Enzymic reactions In food packaging technology, knowledge of enzyme action is essential to a fuller understanding of the implications of different forms of packaging. The importance of enzymes to the food processor is often determined by the conditions prevailing within and outside the food. Control of these conditions is necessary to control enzymic activity during food processing and storage. The major factors useful in controlling enzyme activity are temperature, aw, pH, chemicals that can inhibit enzyme action, alteration of substrates, alteration of products, and preprocessing control. Three of these factors are particularly relevant in a packaging context. The first is temperature i.e. the ability of a package to maintain a low product temperature and thus retard enzyme action will often increase product shelf life. The second important factor is aw, because the rate of enzyme activity is dependent on the amount of water available, low levels of water can severely restrict enzymic activities and even alter the pattern of activity. Finally, alteration of substrate (in particular, the ingress of O 2 into a package) is important in many O2 dependent reactions that are catalyzed by enzymes, for example, enzymic browning due to oxidation of phenols in fruits and vegetables. 1.3.4 Chemical reactions 7 www.Agrimoon.Com Food Packaging Technology Many of the chemical reactions that occur in foods can lead to deterioration in food quality (both nutritional and sensory) or the impairment of food safety. Such reaction classes can involve different reactants or substrates, depending on the specific food and the particular conditions for processing or storage. The rates of these chemical reactions are dependent on a variety of factors amenable to control by packaging, including light, O2 concentration, temperature, and aw. Therefore, the package can, in certain circumstances, play a major role in controlling these factors, and thus indirectly the rate of the deteriorative chemical reactions. The two major chemical changes that occur during the processing and storage of foods and lead to deterioration in sensory quality are lipid oxidation and nonenzymic browning (NEB). Chemical reactions are also responsible for changes in the color and flavor of foods during processing and storage. 1.3.4.1 Lipid oxidation Autoxidation is the reaction of molecular O2 by a free radical mechanism with hydrocarbons and other compounds. The reaction of free radicals with O 2 is extremely rapid, and many mechanisms for initiation of free radical reactions have been described. The crucial role that autoxidation plays in the development of undesirable flavors and aromas in foods is well documented, and autoxidation is a major cause of food deterioration. 1.3.4.2 Nonenzymic browning Nonenzymic browning (NEB) is one of the major deteriorative chemical reactions that occur during storage of dried and concentrated foods. The NEB or Maillard, reaction can be divided into following three stages. (1) Early maillard reactions involving a simple condensation between an aldehyde (usually a reducing sugar) and an amine (usually a protein or amino acid) without browning. (2) Advanced maillard reactions that lead to the formation of volatile or soluble substances (3) Final maillard reactions leading to insoluble brown polymers. 1.3.4.3 Color changes Acceptability of color in a given food is influenced by many factors, including cultural, geographical and sociological aspects of the population. However, regardless of these many factors, certain food groups are acceptable only if they fall within a certain color range. The color of many foods is due to the presence of natural pigments such as chlorophylls, anthocyanins, carotenoids, flavonoids, and myoglobin. 1.3.4.4 Flavor changes In fruits and vegetables, enzymically generated compounds derived from long-chain fatty acids play an extremely important role in the formation of characteristic flavors. In addition, these types of reactions can lead to important off-flavors. Enzyme-induced oxidative breakdown of unsaturated fatty acids occurs extensively in plant tissues, and 8 www.Agrimoon.Com Food Packaging Technology this yields characteristic aromas associated with some ripening fruits and disrupted tissues. Aldehydes and ketones are the main volatiles from autoxidation, and these compounds can cause painty, fatty, metallic, papery, and candle like flavors in foods when their concentrations are sufficiently high. However, many of the desirable flavors of cooked and processed foods derive from modest concentrations of these compounds. The permeability of packaging materials is of importance in retaining desirable volatile components within packages and in preventing undesirable components entering the package from the ambient atmosphere. 1.3.4.5 Nutritional changes The four major factors that influence nutrient degradation and can be controlled to varying extents by packaging are light, O2 concentration, temperature, and aw. However, because of the diverse nature of the various nutrients as well as the chemical heterogeneity within each class of compounds and the complex interactions of these variables, generalizations about nutrient degradation in foods are unhelpful. 1.3.5 Physical changes The physical properties of foods can be defined as those properties that lend themselves to description and quantification by physical rather than chemical means and include geometrical, thermal, optical, mechanical, rheological, electrical, and hydrodynamic properties. Geometrical properties encompass the parameters of size, shape, volume, density, and surface area as related to homogeneous food units, as well as geometrical texture characteristics. Although many of these physical properties are important and must be considered in the design and operation of a successful packaging system, in the present context the focus is on undesirable physical changes in packaged foods. 1.3.6 Microbiological changes Microorganisms can make both desirable and undesirable changes to the quality of foods, depending on whether they are introduced as an essential part of the food preservation process or arise adventitiously and subsequently grow to produce food spoilage. Every microorganism has a limiting aw value below which it will not grow, form spores, or produce toxic metabolites. Water activity can influence each of the four main growths cycle phases by its effect on the germination time, the length of the lag phase and the growth rate phase, the size of the stationary population, and the subsequent death rate. Whether a microorganism survives or dies in a low aw environment is influenced by intrinsic factors that are also responsible for its growth at higher a w. These factors include water-binding properties, nutritive potential, pH, Eh, and the presence of antimicrobial compounds. Microbial growth and survival are not entirely ascribed to reduce aw but are also attributable to the nature of the solute. Key extrinsic factors relating to aw that influence microbial deterioration in foods include temperature, O 2, and chemical treatments. These factors can combine in a complex way to encourage or discourage microbial growth. 9 www.Agrimoon.Com Food Packaging Technology Lesson- 2. Spoilage mechanism during storage 2. Introduction The nature of the deteriorative reactions in foods and the factors that control the rates of these reactions will be briefly outlined. Deteriorative reactions can be enzymic, chemical, physical, and biological. Biochemical, chemical, physical, and biological changes occur in foods during processing and storage, and these combine to affect food quality. The most important quality-related changes are as follows:  Chemical reactions, mainly due to either oxidation or nonenzymic browning reactions.  Microbial reactions, microorganisms can grow in foods. In the case of fermentation this is desired; otherwise, microbial growth will lead to spoilage and, in the case of pathogens, to unsafe food.  Biochemical reactions, many foods contain endogenous enzymes that can potentially catalyze reactions leading to quality loss (enzymic browning, lipolysis, proteolysis, and more). In the case of fermentation, enzymes can be exploited to improve quality.  Physical reactions, many foods are heterogeneous and contain particles. These particles are unstable, and phenomena such as coalescence, aggregation, and sedimentation usually lead to quality loss. The interactions of intrinsic and extrinsic factors affect the likelihood of the occurrence of reactions or processes that affect shelf life. These shelf life limiting reactions or processes can be classified as: chemical/biochemical, microbiological and physical. The effects of these factors are not always detrimental and in some instances they are essential for the development of the desired characteristics of a product. Table: 2.1 Example Type Consequences Color, taste and aroma, nutritive value, Nonenzymic Chemical reaction formation of toxicologically suspect browning (Maillard reaction) compounds (acrylamide) Loss of essential fatty acids, rancid flavor, Fat oxidation Chemical reaction formation of toxicologically suspect compounds 10 www.Agrimoon.Com Food Packaging Technology Biochemical reaction Off-flavors, mainly due to formation of Fat oxidation (lipoxygenase) aldehydes and ketones Hydrolysis Chemical reaction Changes in flavor, vitamin content Formation of free fatty acids and Biochemical reaction Lipolysis (lipase) peptides, bitter taste Formation of amino acids and peptides, Biochemical reaction Proteolysis bitter taste, flavor compounds, changes in (proteases) texture Enzymic Biochemical reaction of Browning browning polyphenols Separation Physical reaction Sedimentation, creaming Combination of chemical Gelation Gel formation, texture changes and physical reaction 2.2. Chemical/biochemical processes Many important deteriorative changes can occur as a result of reactions between components within the food, or between components of the food and the environment. Chemical reactions will proceed if reactants are available and if the activation energy threshold of the reaction is exceeded. The rate of reaction is dependent on the concentration of reactants and on the temperature and/or other energy, e.g. light induced reactions. A general assumption is that for every 10°C rise in temperature, the rate of reaction doubles. Specialized proteins called enzymes catalyse biochemical reactions. 2.3. Oxidation A number of chemical components of food react with oxygen affecting the colour, flavor, nutritional status and occasionally the physical characteristics of foods. In some cases, the effects are deleterious and limit shelf life, in others they are essential to achieve the desired product characteristics. Packaging is used to 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. Estimates of the maximum oxygen tolerance of foods are useful to determine the oxygen permeability of packaging materials required to meet a desired shelf life. 11 www.Agrimoon.Com Food Packaging Technology Foods containing a high percentage of fats, particularly unsaturated fats, are susceptible to oxidative rancidity and changes in flavor. Saturated fatty acids oxidize 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 catalyzed by lipoxygenase. In milk chocolate, the presence of tocopherol (vitamin E), a natural antioxidant in cocoa liquor provides a high degree of protection against rancidity. However, white chocolate does not have the antioxidant protection of cocoa liquor and so is prone to oxidative rancidity, particularly light induced. 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. Oxidation of lycopene, a red/orange carotenoid pigment in tomatoes, causes an adverse colour change from red to brown and affects flavor. In canned tomato products this can be minimized by using plain unlacquered cans. The purpose of the tin coating is to provide protection of the underlying steel, but it also provides a chemically reducing environment within the can. Tomato ketchup used to suffer from black neck – the top of the ketchup in contact with oxygen in the headspace turned black. To disguise this, a label was placed around the neck of the bottle, hiding the discoloration. It has since been shown that oxidation depends on the level of iron in the ketchup and blackening has now been prevented. 2.4. 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. Immature products such as peas and beans have much higher respiration rates and shorter shelf life than products that are mature storage organs such as potatoes and onions. Respiration is the metabolic process whereby sugars and oxygen are converted to more usable sources of energy for living cells. Highly organized and controlled biochemical pathways promote this metabolic process. In non-storage tissues where there are few reserves, such as lettuce and spinach, or immature flower crops such as broccoli, this effect is even greater. Use of temperature control reduces the respiration rate, extending the life of the product. Temperature control combined with MAP further suppresses the growth of yeasts, moulds and bacteria, extending shelf life further. 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. 2.5. 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- 12 www.Agrimoon.Com Food Packaging Technology products such as gases or acids. They may release extra-cellular enzymes (e.g. amylases, lipases, proteases) that affect the texture, flavor, odor 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. In canning, low acid foods are filled into containers that are hermetically sealed and sterilized, typically at 115.5–1210C or above, to ensure all pathogens, especially Clostridium botulinum, are destroyed. Low temperatures might inhibit the growth of an organism and affects its rate of growth. Some microorganisms are adapted to grow at chill temperatures, hence the composition of organisms in the natural microflora will change. 2.6. Physical and physico-chemical processes Many packaging functions such as protection of the product from environmental factors and contamination such as dust and dirt, dehydration and rehydration, insect and rodent infestation, containment of the product to avoid leakage and spillage, and physical protection action against hazards during storage and distribution are taken for granted by the consumer. Packaging is very often the key factor to limiting the effects of physical damage on product shelf life. Different forms of this process is Physical damage  Insect damage  Moisture changes  Barrier to odor pick-up 2.7. 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. 13 www.Agrimoon.Com Food Packaging Technology Module- 2 Definition, requirement, importance and scope of packaging of foods, types and classification of packaging system, advantage of modern packaging system Lesson- 3 Functions of food packaging 3.1. Introduction Packaging is an industrial and marketing technique for containing, protecting, identifying and facilitating the sale and distribution of agricultural, industrial and consumer products. Or The packaging institute international defines packaging as a enclosure of products, items or packages in a wrapped pouch, bag, box, cup, tray, can, tube, bottle or other container form to perform one or more of the following functions as containment, protection and /or preservation, communications and utility or performance. If the device or container performs one or more of these functions it is considered as a package. The UK Institute of packaging provides three definitions of packaging. (a) A coordinated system of preparing goods for transport, distribution, storage, retailing and end-use. (b) A means of ensuring safe delivery to the ultimate consume in sound condition at minimum cost. (c) A techno-economic function aimed at minimizing cost of delivery while maximizing sales. 3.2. Basic functions of packaging Efficient packaging is a necessity for every kind of food, whether it is fresh or processed.It is an essential link between the food producer and the consumer, and unless performed correctly the standing of the product suffers and customer goodwill is lost. The basic functions of packaging are more specifically stated. 3.2.1. Containment The containment function involves the ability of the packaging to maintain its integrity during the handling involved in filling, sealing, processing (in some cases, such as retorted, irradiated, and high-pressure-processed foods), transportation, marketing, and dispensing of the food. 3.2.2 Protection The need for protection depends on the food product but generally includes prevention of biological contamination (from microorganisms, insects, rodents), oxidation (of lipids, flavors, colors, vitamins, etc.), moisture change (which affects microbial growth, oxidation rates, and food texture), aroma loss or gain, and physical damage (abrasion, fracture, 14 www.Agrimoon.Com Food Packaging Technology and/or crushing). Protection can also include providing tamper evident features on the package. In providing protection, packaging maintains food safety and quality achieved by refrigeration, freezing, drying, heat processing, and other preservation of foods. 3.2.3 Communication The information that a package provides involves meeting both legal requirements and marketing objectives. Food labels are required to provide information on the food processor, ingredients (including possible allergens in simple language), net content, nutrient contents, and country of origin. Package graphics are intended to communicate product quality and, thus, sell the product. Bar codes allow rapid check-out and tracking of inventory. Other package codes allow determination of food production location and date. Various open dating systems inform the consumer about the shelf life of the food product. Plastic containers incorporate a recycling code for identification of the plastic material. 3.2.4 Preservation Product protection is the most important function of packaging. Protection means the establishment of a barrier between the contained product and the environment that competes with man for the product. 3.2.5 Convenience Providing convenience (sometimes referred to as utility of use or functionality) to consumers has become a more important function of packaging. Range of sizes, easy handling, easy opening and dispensing, resealability, and food preparation in the package are examples of packaging providing convenience to the consumer. 3.2.6 Unitization Unitization is assembly or grouping of a number of individual items of products or packages into a single entity that can be more easily distributed, marketed, or purchased as a single unit. For example: a paperboard folding carton containing three flexible material pouches of seasoning or soup mix delivers more product to a consumer than does a single pouch. A paperboard carton wrapped around 12 beer bottles provides more desired liquid refreshment for home entertainment than does an attempt to carry individual bottles in one‘s hands. Unitization reduces the number of handlings required in physical distribution and, thus, reduces the potential for damage. Because losses in physical distribution are significantly reduced with unitization, significant reductions in distribution costs are affected. 3.2.7Information about the product Packaging is one of the major communications media. Usually overlooked in the measured media criteria, packaging is the main communications link between the consumer or user and the manufacturer, at both the point of purchase and the point of use. Packaging educates consumers about requirements, product ingredients and uses etc. 3.2.8 Presentation 15 www.Agrimoon.Com Food Packaging Technology Material type, shape, size, colour and merchandising display units etc. of packaging improve display of food. 3.2.9Brand communication Packaging provides brand communication to the consumers by the use of typography, symbols, illustrations, advertising and colour, thereby creating visual impact. 3.2.10 Promotion Packaging helps to promote the food as it informs to consumers about many offers i.e. free extra product, new product, money off etc. 3.2.11 Economy The package is also an important part of the manufacturing process and must be efficiently filled, closed, and processed at high speeds in order to reduce costs. It must be made of materials which are rugged enough to provide protection during distribution but be of low enough cost for use with foods. Packaging costs, which include the materials as well as the packaging machinery, are a significant part of the cost of manufacturing foods, and in many cases, these costs can be greater than the cost of the raw ingredients used to make the food. Therefore, packaging materials must be economical, given the value of the food product. 3.3 Other functions of packaging Other functions of packaging include apportionment of the product into standard units of weight, measure, or quantity prior to purchase. Yet another objective is to facilitate product use by the consumer with devices such as spouts, squeeze bottles, and spray cans. Aerosols not only serve as dispensers, but also prepare the product for use, such as aerating the contained whip toppings. Still other forms of packaging are used in further preparation of the product by the consumer, for example tea bags that are plastic-coated, porous paper pouches, or frozen dinner trays, which were originally aluminum and now are fabricated from other materials such as crystallized polyester and polyester-coated paperboard. 3.4 Requirements for effective food packaging Some of the important general requirements of food packages are given below 16 www.Agrimoon.Com Food Packaging Technology  Be nontoxic  Protect against contamination from microorganisms  act as a barrier to moisture loss or gain and oxygen ingress  protect against ingress of odors or environmental toxicants  Filter out harmful UV light  Provide resistance to physical damage  Be transparent (8) be tamper – resistant or tamper – evident  Be easy to open  Have dispensing and resealing features  Be disposed of easily,  Meet size, shape and weight requirements  Have appearance, printability features  Be low cost  Be compatible with food  Have special features such as utilizing groups of product together. 17 www.Agrimoon.Com Food Packaging Technology Lesson- 4 Packaging systems 4.1 Aseptic packaging Aseptic packaging is a method in which food is sterilized or commercially sterilized outside of the can, usually in a continuous process, and then aseptically placed in previously sterilized containers which are subsequently sealed in an aseptic environment. After cooling, the sterile food product is pumped to an aseptic packaging system where the food is filled and hermetically sealed into previously sterilized containers. Aseptically processed foods can be packaged in the same types of containers used for retorted foods. However, another advantage of aseptically processed foods is that they can be packaged in containers that do not have to survive the conditions of a retort. These include LDPE/Pb/LDPE/AL/LDPE laminate cartons and multilayer plastic flexible packaging that has cost and convenience advantages. The disadvantage of these packages is that they are not as easily recycled as metal and glass containers. Aseptic filling systems have also been developed for HDPE and PET bottles. Aseptic filling of PET containers may have a cost advantage over hot filling of heat-set PET containers. Another advantage of aseptically processed foods is that they can be filled into drums, railroad tank cars, tank trucks and silos that have been previously sterilized with steam. The food can be later reprocessed and packaged to meet market demands. The sterilization agents available for aseptic packaging include heat, chemical treatment with hydrogen peroxide and high energy irradiation (UV light or ionizing (gamma) irradiation). A combination of hydrogen peroxide and mild heat is most commonly used with plastic and paperboard-based laminate packaging. The most commercially successful form of aseptic packaging utilizes paper and plastic materials which are sterilizes, formed, filled and sealed in continuous operation. The package may be sterilized with heat or combination of heat and chemicals. In some cases, the disinfectant property of hydrogen peroxide (H 2O2) is combined with heated air or ultra violet light to make lower temperatures effective in sterilizing these less heat resistant packaging materials. Aseptic packaging is also used with the metal cans as well as large plastic and metal drums or large flexible pouches. Great quantities of food materials are used as intermediates in the production of further processed foods. This frequently requires packaging of such items as tomato paste or apricot puree in large containers. The food manufacturer then may use the tomato paste in the production of ketchup or the apricot puree in bakery products. If such large volumes were to be sterilized in drums, by the time the cold point reached sterilization temperature the product nearer the drum walls would be excessively burned. Such items can be quickly sterilized in efficient heat exchangers and aseptically packaged. 4.2 Modified Atmosphere Packaging Modified atmosphere packaging (MAP) is a procedure which involves replacing air inside a package with a predetermined mixture of gases prior to sealing it. Once the package is sealed, no further control is exercised over the composition of the in-package atmosphere. 18 www.Agrimoon.Com Food Packaging Technology However, this composition may change during storage as a result of respiration of the contents and/or solution of some of the gas in the product. Vacuum packaging is a procedure in which air is drawn out of the package prior to sealing but no other gases are introduced. This technique has been used for many years for products such as cured meats and cheese. It is not usually regarded as a form of MAP. The gases involved in modified atmosphere packaging, as applied commercially are carbon dioxide, nitrogen and oxygen. Carbon dioxide reacts with water in the product to form carbonic acid which lowers the pH of the food. It also inhibits the growth of certain microorganisms, mainly moulds and some aerobic bacteria. Lactic acid bacteria are resistant to the gas and may replace aerobic spoilage bacteria in modified atmosphere packaged meat. Most yeasts are also resistant to carbon dioxide. Anaerobic bacteria, including food poisoning organisms, are little affected by carbon dioxide. Consequently, there is a potential health hazard in MAP products from these microorganisms. Moulds and some gram negative, aerobic bacteria, such as Pseudomonas spp, are inhibited by carbon dioxide concentrations in the range 5–50%. In general, the higher the concentration of the gas, the greater is its inhibitory power. The inhibition of bacteria by carbon dioxide increases as the temperature decreases. Nitrogen has no direct effect on microorganisms or foods, other than to replace oxygen, which can inhibit the oxidation of fats. As its solubility in water is low, it is used as a bulking material to prevent the collapse of MAP packages when the carbon dioxide dissolves in the food. This is also useful in packages of sliced or ground food materials, such as cheese, which may consolidate under vacuum. Oxygen is included in MAP packages of red meat to maintain the red colour, which is due to the oxidation of the myoglobin pigments. It is also included in MAP packages of white fish, to reduce the risk of botulism. Other gases have antimicrobial effects. Carbon monoxide will inhibit the growth of many bacteria, yeasts and moulds, in concentrations as low as 1%. However, due to its toxicity and explosive nature, it is not used commercially. Sulphur dioxide has been used to inhibit the growth of moulds and bacteria in some soft fruits and fruit juices. Argon, helium, xenon and neon, have also been used in MAP of some foods. MAP packages are either thermoformed trays with heat-sealed lids or pouches. With the exception of packages for fresh produce, these trays and pouches need to be made of materials with low permeability to gases (CO2, N2, and O2). Laminates are used, made of various combinations of polyester (PET), polyvinylidene chloride (PVdC), polyethylene (PE) and polyamide. 4.3 Active packaging Active packaging refers to the incorporation of certain additives into packaging film or within packaging containers with the aim of maintaining and extending product shelf life. Packaging may be termed active when it performs some desired role in food preservation other than providing an inert barrier to external conditions. Active packaging includes additives or ‗freshness enhancers‘ that are capable of scavenging oxygen, adsorbing carbon dioxide, moisture, ethylene and/or flavor/odor taints, releasing ethanol, sorbates, antioxidants and/or other preservatives and/or maintaining temperature control. Table 19 www.Agrimoon.Com Food Packaging Technology 2.1 lists examples of active packaging systems, some of which may offer extended shelf life opportunities for new categories of food products. Table 4.1 Selected active packaging systems S.N. Systems Mechanisms Food application 1. Iron-based Bread, cakes, cooked rice, 2. Metal/acid biscuits, pizza, pasta, cheese, 3. Metal (e.g. platinum) 1. Oxygen scavengers cured meats, cured fish, catalyst coffee, 4. Ascorbate/metallic salts snack foods, dried foods 5. Enzyme-based and beverages 1. Iron oxide/calcium hydroxide 2. Ferrous carbonate/metal Coffee, fresh meats, fresh fish, Carbon dioxide halide scavengers/ 2. nuts, other snack food 3. Calcium oxide/activated products emitters charcoal and sponge cakes 4. Ascorbate/sodium bicarbonate 1. Potassium permanganate Fruit, vegetables and other Ethylene 3. 2. Activated carbon scavengers horticultural products 3. Activated clays/zeolites 1. Organic acids Cereals, meats, fish, bread, 4. 2. Silver zeolite Preservative cheese, snack foods, fruit releasers and 3. Spice and herb extracts vegetables 4. BHA/BHT antioxidants 20 www.Agrimoon.Com Food Packaging Technology 5. Vitamin E antioxidant 6. Volatile chlorine dioxide/ sulphur dioxide Pizza crusts, cakes, bread, 1. Alcohol spray biscuits, 5. Ethanol emitters 2. Encapsulated ethanol fish and bakery products 1. PVA blanket Fish, meats, poultry, snack 2. Activated clays and foods, cereals, dried foods, 6. Moisture absorbers minerals sandwiches, fruit and vegetables 3. Silica gel 1. Cellulose triacetate 2. Acetylated paper Fruit juices, fried snack foods, 3. Citric acid Flavour/odour 7. adsorbers fish, cereals, poultry, dairy 4. Ferrous salt/ascorbate products and fruit 5. Activated carbon/clays/ zeolites 1. Non-woven plastics 2. Double-walled containers Temperature Ready meals, meats, fish, control 8. 3. Hydro fluorocarbon gas poultry and beverages packaging 4. Lime/water 5. Ammonium nitrate/water The shelf life of packaged food is dependent on numerous factors, such as the intrinsic nature of the food (e.g. pH, water activity, nutrient content, occurrence of antimicrobial compounds, redox potential, respiration rate, biological structure) and extrinsic factors (e.g. storage temperature, relative humidity, surrounding gaseous composition). These factors directly influence the chemical, biochemical, physical and microbiological spoilage mechanisms of individual food products and their achievable shelf life. By carefully considering all of these factors, it is possible to evaluate existing and developing active 21 www.Agrimoon.Com Food Packaging Technology packaging technologies and apply them for maintaining the quality and extending the shelf life of different food products. 22 www.Agrimoon.Com Food Packaging Technology Lesson- 5 Modern Packaging System 5.1 Introduction Various terms for new packaging methods can be found in the literature, such as active, smart, interactive, clever or intelligent packaging. The definitions of active and intelligent packaging are  Active packaging changes the condition of the packed food to extend shelflife or to improve safety or sensory properties, while maintaining the quality of the packaged food.  Intelligent packaging systems monitor the condition of packaged foods to give information about the quality of the packaged food during transport and storage. 5.2 Active packaging Active packaging refers to the incorporation of certain additives into packaging film or within packaging containers with the aim of maintaining and extending product shelf life. Packaging may be termed active when it performs some desired role in food preservation other than providing an inert barrier to external conditions. Active packaging includes additives or ‗freshness enhancers‘ that are capable of scavenging oxygen, adsorbing carbon dioxide, moisture, ethylene and/or flavor/odor taints, releasing ethanol, sorbates, antioxidants and/or other preservatives and/or maintaining temperature control. Active packaging techniques for preservation and improving quality and safety of foods can be divided into three categories; absorbers (i.e. scavengers, releasing systems and other systems. Absorbing (scavenging) systems remove undesired compounds such as oxygen, carbon dioxide, ethylene, excessive water, taints and other specific compounds. Releasing systems actively add or emit compounds to the packaged food or into the head- space of the package such as carbon dioxide, antioxidants and preservatives. Other systems may have miscellaneous tasks, such as self-heating, self-cooling and preservation. The main active packaging systems are: 5.2.1 Oxygen scavenger: The most common oxygen scavengers take the form of small sachets containing various iron-based powders containing an assortment of catalysts. These chemical systems often react with water supplied by the food to produce a reactive hydrated metallic reducing agent that scavenges oxygen within the food package and irreversibly converts it to a stable oxide. The iron powder is separated from the food by keeping it in a small, highly oxygen permeable sachet. 5.2.2 Carbon Dioxide Scavengers/Emitters There are many commercial sachet and label devices that can be used to either scavenge or emit carbon dioxide. The use of carbon dioxide scavengers is particularly applicable for fresh roasted or ground coffees that produce significant volumes of carbon dioxide. Fresh 23 www.Agrimoon.Com Food Packaging Technology roasted or ground coffees cannot be left unpackaged since they absorb moisture and oxygen and lose desirable volatile aromas and flavors. 5.2.3 Ethylene Scavengers Ethylene (C2H4) is a plant hormone that accelerates the respiration rate and subsequent senescence of horticultural products such as fruit, vegetables and flowers. Many of the effects of ethylene are necessary, e.g. induction of flowering in pineapples and colour development in citrus fruits, bananas and tomatoes, but in most horticultural situations it is desirable to remove ethylene or to suppress its effects. Effective systems utilize potassium permanganate (KMnO4) immobilized on an inert mineral substrate such as alumina or silica gel. KMnO4 oxidizes ethylene to acetate and ethanol and in the process a change colour from purple to brown and hence indicates its remaining ethylene-scavenging capacity. KMnO4-based ethylene scavengers are available in sachets to be placed inside produce packages or inside blankets or tubes that can be placed in produce storage warehouses. 5.2.4 Ethanol Emitters The use of ethanol as an antimicrobial agent is well documented. It is particularly effective against mould but can also inhibit the growth of yeasts and bacteria. Ethanol can be sprayed directly onto food products just prior to packaging. The size and capacity of the ethanol-emitting sachet used depends on the weight of food, aw of the food and the shelf life required. When food is packed with an ethanol-emitting sachet, moisture is absorbed by the food and ethanol vapor is released and diffuses into the package headspace. 5.2.5 Preservative Releasers One most commonly used preservative releaser is a synthetic silver zeolite that has been directly incorporated into food contact packaging film. The purpose of the zeolite is apparently to allow slow release of antimicrobial silver ions into the surface of food products. Many other synthetic and naturally occurring preservatives have been proposed and/or tested for antimicrobial activity in plastic and edible films. These include organic acids, e.g. propionate, benzoate and sorbate, bacteriocins, e.g. nisin„ spice and herb extracts, e.g. from rosemary, cloves, horseradish, mustard, cinnamon and thyme, enzymes, e.g. peroxidase, lysozyme and glucose oxidase, chelating agents, e.g. EDTA, inorganic acids, e.g. sulphur dioxide and chlorine dioxide, and anti-fungal agents, e.g. imazalil and benomyl. The major potential food applications for antimicrobial films include meats, fish, bread, cheese, fruit and vegetables. 5.2.6 Moisture Absorbers Excess moisture is a major cause of food spoilage. Soaking up moisture by using various absorbers or desiccants is very effective at maintaining food quality and extending shelf life by inhibiting microbial growth and moisture-related degradation of texture and flavor. Moisture absorber sachets for humidity control in packaged dried foods, several companies manufacture moisture drip absorbent pads, sheets and blankets for liquid 24 www.Agrimoon.Com Food Packaging Technology water control in high aw foods such as meats, fish, poultry, fruit and vegetables are available. 5.2.7 Flavour/Odor Adsorbers The interaction of packaging with food flavors and aromas has long been recognized, especially through the undesirable flavor scalping of desirable food components. Two types of taints amenable to removal by active packaging are amines, which are formed from the breakdown of fish muscle proteins, and Aldehydes that are formed from the autoxidation of fats and oils. Volatile amines with an unpleasant smell, such as trimethylamine, associated with fish protein breakdown are alkaline and can be neutralized by various acidic compounds. The bags that are made from film containing a ferrous salt and an organic acid such as citrate or ascorbate are claimed to oxidize amines when they are absorbed by the polymer film. Odor and Taste Control (OTC) technology removes or neutralizes aldehydes. 5.3 Intelligent packaging Intelligent packaging includes indicators to be used for quality control of packed food. They can be so-called external indicators, i.e., indicators which are attached outside the package (time temperature indicators), and so-called internal indicators which are placed inside the package, either to the head-space of the package or attached into the lid. 5.3.1 Time temperature indicator (TTI) A time temperature indicator (TTI) can be defined as a simple device that can give the idea about easily measurable, time-temperature dependent change which affects full or partial temperature history of a food product to which it is connected. The principles of TTI operation are based on mechanical, chemical, electrochemical, enzymatic or microbiological irreversible change. 5.3.2 Freshness indicators Two types of the changes can take place in the fresh food product i.e. (i) Microbiological growth and metabolism resulting in pH changes, formation of toxic compounds, off-odors, gas and slime formation, (ii) Oxidation of lipids and pigments resulting in undesirable flavors, formation of compounds with adverse biological reactions or discoloration. A freshness indicator indicates directly the quality of the product. The indication of microbiological quality is based on a reaction between the indicator and the metabolites produced during growth of microorganisms in the product. An indicator that would show specifically the spoilage or the lack of freshness of the product, in addition to temperature abuse or package leaks, would be ideal for the quality control of packed products. 5.3.3 Pathogen indicators Commercially available Toxin Guard TM is a system to build polyethylene-based packaging material, which is able to detect the presence of pathogenic bacteria with the aid of 25 www.Agrimoon.Com Food Packaging Technology immobilized antibodies. As the analyte (toxin, microorganism) is in contact with the material it will be bound first to a specific, labelled antibody and then to a capturing antibody printed as a certain pattern. The method could also be applied for the detection of pesticide residues or proteins resulting from genetic modifications. 26 www.Agrimoon.Com Food Packaging Technology Module- 3 Different types of packaging materials used Lesson- 6 Paper/Paperboard 6.1. Introduction Pulp is the raw material for the production of paper, paperboard, corrugated board and similar manufactured products. It is obtained from plant fiber and is therefore a renewable resource. Today about 97 percent of the world's paper and board is made from wood pulp, and about 85 percent of the wood pulp used in from spruces, firs and pines – coniferous trees that predominate in the forests of the North Temperate Zone. There are three main constituents of wood cell wall:  Cellulose This is a long chain, linear polymer built-up of a large numbers of glucose molecules and is the most abundant, naturally occurring organic compound. Cellulose is moderately resistant to the action of chlorine and dilute sodium hydroxide under mild conditions, but is modified or dissolved under more severe conditions. It is relatively resistant to oxidation and therefore bleaching operations can be used to remove small amounts of impurities such as lignin without appreciable damage to the strength of the pulp.  Hemicelluloses These are lower molecular weight mixed sugar polysaccharides consisting of one or more of the following molecules: Xylose, mannose, arabivose, and glactose. Hemicelluloses are usually soluble in dilute alkalis.  Lignin This is highly branched, thermoplastic polymer of uncertain size, built up largely from substituted phenyl-propane units. It has no fiber forming properties and is attacked by chlorine and sodium hydroxide with formation of soluble, dark brown derivatives. It softens at about 160oC. The principal differences between paper, paperboard and fiberboard are thickness and use. Paper are thin, flexible and used for bags and wraps, paperboard is thicker, more rigid and used to construct single layer cartons, fiberboard is made by combining layers of strong papers and is used to construct secondary shipping cartons. Paper from wood pulp is bleached and coated or impregnated with waxes, resins, lacquers, plastics and laminations of aluminum to improve its strength, especially in high humidity environments such as are often found around foods. Acid treatment of paper pulp modifies the cellulose and gives rise to water and oil resistant parchments of considerable wet strength. These papers are called greaseproof or glassine papers and are characterized by long wood pulp fibers which imparts increased physical strength. Kraft paper is the strongest of papers and in its unbleached form is commonly used for grocery bags. If bleached and coated, it is commonly used as butcher warp. The word Kraft comes from the German word for strong. Acid treatment of paper pulp modifies the cellulose and gives rise to water and oil resistant parchments of considerable wet strength. 27 www.Agrimoon.Com Food Packaging Technology These papers are called greaseproof or glassine papers and are characterized by long wood pulp fibers which impart increased physical strength. Papers and paperboards used for packaging range from thin tissues to thick boards. The main examples of paper and paperboard based packaging are: 1. paper bags, wrapping, packaging papers and infusible tissues, e.g. tea and coffee bags, sachets, pouches, overwrapping paper, sugar and flour bags, carrier bags 2. multiwall paper sacks 3. folding cartons and rigid boxes 4. corrugated and solid fiberboard boxes (shipping cases) 5. paper based tubes, tubs and composite containers 6. fire drums 7. liquid packaging 8. moulded pulp containers 9. labels 10. sealing tapes 11. cushioning materials 12. cap liners (sealing wads) and diaphragms (membranes). Paper and paperboard packaging is used over a wide temperature range, from frozen food storage to the high temperatures of boiling water and heating in microwave and conventional radiant heat ovens. Whilst it is approved for direct contact with many food products, packaging made solely from paper and paperboard is permeable to water, water vapor, aqueous solutions and emulsions, organic solvents, fatty substances (except grease resistant paper grades), gases, such as oxygen, carbon dioxide and nitrogen, aggressive chemicals and to volatile flavors and aromas. Whilst it can be sealed with several types of adhesive, it is not, itself, heat sealable. Paper and paperboard, however, can acquire barrier properties and extended functional performance, such as heat sealability for leak-proof liquid packaging, through coating and lamination with plastics, such as polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET or PETE) and ethylene vinyl alcohol (EVOH), and with aluminum foil, wax, and other treatments. Packaging made solely from paperboard can provide a wide range of barrier properties by being overwrapped with a heat sealable plastic film such as polyvinylidene chloride (PVdC) coated oriented polypropylene (OPP or BOPP). 6.2. Properties of paper and paperboard The features of paper and paperboard which make these materials suitable for packaging relate to appearance and performance. These features are determined by the type of paper and paperboard – the raw materials used and the way they have been processed. Appearance and performance can be related to measurable properties which are controlled in the selection of raw materials and the manufacturing process. 28 www.Agrimoon.Com Food Packaging Technology 6.2.1. Appearance Appearance relates to the visual impact of the pack and can be expressed in terms of colour, smoothness and whether the surface has a high or low gloss (matte) finish. Colour depends on the choice of fibre for the outer surface, and also, where appropriates, the reverse side. As described above, the choice is either white, brown or grey. In addition some liners for corrugated board comprise a mix of bleached and brown fibers. Other colors are technically possible either by using fibers dyed to a specific colour or coated with a mineral pigment colored coating. 6.2.2. Performance Performance properties are related to the level of efficiency achieved during the manufacture of the pack, in printing, cutting and creasing, gluing and the packing operation. Performance properties are also related to pack compression strength in storage, distribution, at the point of sale and in consumer use. Specific measurable properties include stiffness, short span compression (rigidity) strength, tensile strength, wet strength, % stretch, tear strength, fold endurance, puncture resistance and ply bond strength. Other performance properties relate to moisture content, air permeability, water absorbency, surface friction, surface tension, ink absorbency etc. Chemical properties include pH, whilst chloride and sulphate residues are relevant for aluminum foil lamination. Flatness is easily evaluated but is a complicated issue as lack of flatness can arise from several potential causes, from the hygrosensitivity characteristics of the fibre, manufacturing variables and handling at any stage including printing and use. Neutrality with respect to odor and taint, and product safety are performance needs which are important in the context of paper and board packaging which is in direct or close proximity to food. 6.3. Types of paper Paper is divided into two broad categories: Fine papers, generally made of bleached pulp, and typically used for writing paper, bond, book and cover papers, and coarse papers, generally made of unbleached Kraft softwood pulps and used for packaging. Main types of packaging papers are: 6.3.1. Kraft paper This is typically a coarse paper with exceptional strength, often made on a fourdrinier machine and then either machine – glazed on a Yankee dryer or machine. 6.3.2. Bleached paper These are manufactured from pulps which are relatively while, bright and soft and receptive to the special chemicals necessary to develop many functional properties. They are generally more expensive and weaker than unbleached papers. Their aesthetic appeal is frequently augmented by day coating on one or both sides. 29 www.Agrimoon.Com Food Packaging Technology 6.3.3. Greaseproof paper This is a translucent, machine finished paper which has been hydrated to give oil and grease resistance. Prolonged beating or mechanical refining is used to break the cellulose fibers which absorb so much water that they become superficially gelatinized and sticky. 6.3.4. Glassine paper Glassine paper derives its name from its glassy, smooth surface, high density and transparency. It is produced by further treating grease proof paper in a super calendar. 6.3.5. Vegetable parchment Vegetable parchment takes its name from its physical similarity to animal parchment, which is made from animal skins. Because of its grease resistance and wet strength, it strips away easily from food material without defibering, thus finding use as an interleaver between slices of food such as meat or pastry. It was first used for wrapping fatty foods such as butter. 6.3.6. Tissue paper Tissue papers range from semitransparent to totally opaque, and can be waxed. They are generally either machine – Finished (MF) or machine – Glazed (MG). MG papers may also be machine finished to improve the smoothness on both sides. 6.3.7. Waxed paper Waxed papers provide a barrier against penetration of liquids and vapors. Wet waxed papers have a continuous surface film on one or both sides achieved by shock-chilling the waxed web immediately after application of the wax. This also imparts a high degree of gloss on the coated surface. Dry waxed papers are produced using heated rolls and do not have a continuous film on the surfaces. Wax-laminated papers are bonded with a continuous film of wax which acts as an adhesive. The primary purpose of the wax is to provide a moisture barrier and a heat sealable laminate. 6.4. Types of paper boards Paperboards are made from the same raw materials as papers. They normally are made on the cylinder machine and consist of two or more layers of different quality pulps. The types of paperboard used in food packaging include: 6.4.1. Chipboard Chipboard is made from a mixture of repulped waste with chemical and mechanical pulp. It is dull grey in colour and relatively weak. It is available lined on one side with unbleached, semi or fully bleached chemical pulp. A range of such paperboards are available, with different quality liners. Chipboards are seldom used in direct contact with foods, but are used as outer cartons when the food is already contained in a film pouch or bag e.g. breakfast cereals. 30 www.Agrimoon.Com Food Packaging Technology 6.4.2. Duplex board Duplex board is made from a mixture of chemical and mechanical pulp, usually lined on both sides with chemical pulp. It is used for some frozen foods, biscuits and similar products. 6.4.3. Solid white board In Solid white board, all plies are made from fully, bleached chemical pulp. It is used for some frozen foods, food liquids and other products requiring special protection. 31 www.Agrimoon.Com Food Packaging Technology Lesson- 7 Glass 7.1. Definition of glass The American Society for Testing Materials defined glass as ‗an inorganic product of fusion which has cooled to a rigid state without crystallizing‘ (ASTM, 1965). The atoms and molecules in glass have an amorphous random distribution. Scientifically this means that it has failed to crystallize from the molten state, and maintains a liquid-type structure at all temperatures. In appearance it is usually transparent but, by varying the components, this can be changed-as also can important properties such as thermal expansion, colour and the pH of aqueous extracts. Glass is hard and brittle, with a chonchoidal (shell-like) fracture. 7.2. Glass Composition Glass is primarily formed from oxides of metals, with the most common being dioxide which is common sand. Glass is made by mixing several naturally-occurring inorganic compounds at a temperature above their melting points. The molten mixture is then cooled to produce a noncrystalline, amorphous solid. The main ingredient is silica (sand) (SiO2) that serves as the network-forming backbone of the glass. However, silica has a very high melting temperature, and molten silica has high viscosity that makes it difficult to form into shapes. Adding soda (Na2O) modifies the silica network by disrupting some of the Si-O bonds, with resulting lower melting temperature and viscosity but reduced resistance to dissolving in water. Thus, lime (CaO) is added as a network stabilizer, with the result that durability is increased but tendency to crystallize is also increased. Finally, alumina (Al2O3) is added as an intermediate to resist crystallization. Minor amounts of colorants are added to produce colored glass, including chromium oxide for green, cobalt oxide for blue, nickel oxide for violet, selenium for red, and iron plus sulfur and carbon for amber. Amber provides the best protection for light-sensitive foods and beverages, transmitting very little light with wavelength shorter than 450 nm. 7.3 Types of glass 7.3.1 White flint (clear glass) Colorless glass, known as white flint, is derived from soda, lime and silica. This composition also forms the basis for all other glass colors. A typical composition would be: silica (SiO2) 72%, from high purity sand; lime (CaO) 12%, from limestone (calcium carbonate); soda (Na2O) 12%, from soda ash alumina (Al2O3), present in some of the other raw materials or in feldspar-type aluminous material; magnesia (MgO) and potash (K2O), ingredients not normally added but present in the other materials. Cullet, recycled broken glass, when added to the batch reduces the use of these materials. 7.3.2 Pale green (half white) Where slightly less pure materials are used, the iron content (Fe 2O3) rises and a pale green glass is produced. Chromium oxide (Cr 2O3) can be added to produce a slightly denser blue green colour. 32 www.Agrimoon.Com Food Packaging Technology 7.3.3 Dark green This colour is also obtained by the addition of chromium oxide and iron oxide. 7.3.4 Amber (brown in various colour densities) Amber is usually obtained by melting a composition containing iron oxide under strongly reduced conditions. Carbon is also added. Amber glass has UV protection properties and could well be suited for use with light-sensitive products. 7.3.5 Blue Blue glass is usually obtained by the addition of cobalt to a low-iron glass. Almost any colored glass can be produced either by furnace operation or by glass colouring in the conditioning forehearth. The latter operation is an expensive way of producing glass and commands a premium product price. Forehearth colors would generally be outside the target price of most carbonated soft drinks. 7.4 Attributes of food packaged in glass containers The glass package has a modern profile with distinct advantages, including: 7.4.1 Quality image Consumer research by brand owners has consistently indicated that consumers attach a high quality perception to glass packaged products and they are prepared to pay a premium for them, for specific products such as spirits and liqueurs. 7.4.2 Transparency It is a distinct advantage for the purchaser to be able to see the product in many cases, e.g. processed fruit and vegetables. 7.4.3 Surface texture Most glass is produced with a smooth surface, other possibilities also exist, for example, for an overall roughened ice-like effect or specific surface designs on the surface, such as text or coats of arms. These effects emanate from the moulding but subsequent acid etch treatment is another option. 7.4.4 Colour A range of colors are possible based on choice of raw materials. Facilities exist for producing smaller quantities of nonmainstream colors. 7.4.5 Decorative possibilities Decorative possibilities including ceramic printing, powder coating, colored and plain printed plastic sleeving and a range of labeling options. 7.4.6 Impermeability All practical purposes in connection with the packaging of food, glass is impermeable. 33 www.Agrimoon.Com Food Packaging Technology 7.4.7 Chemical integrity Glass is chemically resistant to all food products, both liquid and solid. It is odorless. 7.4.8 Design potential Distinctive shapes are often used to enhance product and brand recognition. 7.4.9 Heat processable Glass is thermally stable, which makes it suitable for the hot-filling and the in-container heat sterilization and pasteurization of food products. 7.4.10 Microwaveable Glass is open to microwave penetration and food can be reheated in the container. Removal of the closures is recommended, as a safety measure, before heating commences, although the closure can be left loosely applied to prevent splashing in the microwave oven. Developments are in hand to ensure that the closure releases even when not initially slackened. 7.4.11 Tamper evident Glass is resistant to penetration by syringes. Container closures can be readily tamper- evidenced by the application of shrinkable plastic sleeves or in-built tamper evident bands. Glass can quite readily accept preformed metal and roll-on metal closures, which also provide enhanced tamper evidence. 7.4.12 Ease of opening The rigidity of the container offers improved ease of opening and reduces the risk of closure misalignment compared with plastic containers, although it is recognized that vacuum packed food products can be difficult to open. Technology in the development of lubricants in closure seals, improved application of glass surface treatments together with improved control of filling and retorting all combine to reduce the difficulty of closure removal. However, it is essential in order to maintain shelf life that sufficient closure torque is retained, to ensure vacuum retention with no closure back-off during processing and distribution. 7.4.13 UV protection Amber glass offers UV protection to the product and, in some cases, green glass can offer partial UV protection. 7.4.14 Strength Although glass is a brittle material glass containers have high top load strength making them easy to handle during filling and distribution. While the weight factor of glass is unfavorable compared with plastics, considerable savings are to be made in warehousing and distribution costs. Glass containers can withstand high top loading with minimal secondary packaging. Glass is an elastic material and will absorb energy. 34 www.Agrimoon.Com Food Packaging Technology Lesson- 8 Plastic 8. 0 Introduction Plastic is an organic macromolecular compounds obtained by polymerisation, polycondensation, polyaddition or any similar process from molecules with a lower molecular weight or by chemical alteration of natural macromolecular compounds. Plastics are used in the packaging of food because they offer a wide range of appearance and performance properties which are derived from the inherent features of the individual plastic material and how it is processed and used. Plastics are resistant to many types of compound – they are not very reactive with inorganic chemicals, including acids, alkalis and organic solvents, thus making them suitable, i.e. inert, for food packaging. Plastics do not support the growth of microorganisms. Some plastics may absorb some food constituents, such as oils and fats, and hence it is important that a thorough testing is conducted to check all food applications for absorption and migration. Gases such as oxygen, carbon dioxide and nitrogen together with water vapor and organic solvents permeate through plastics. The rate of permeation depends on:  type of plastic  thickness and surface area  method of processing  concentration or partial pressure of the permeant molecule  storage temperature Plastics have properties of strength and toughness. Polyethylene terephthalate (PET) film has a mechanical strength similar to that of iron, but under load the PET film will stretch considerably more than iron before breaking. 8.1. Application of Plastic in food processing  Plastics are used as containers, container components and flexible packaging. In usage, by weight, they are the second most widely used type of packaging and first in terms of value. Applications of plastic are  rigid plastic containers such as bottles, jars, pots, tubs and trays  flexible plastic films in the form of bags, sachets, pouches and heat-sealable flexible lidding materials  plastics combined with paperboard in liquid packaging cartons  expanded or foamed plastic for uses where some form of insulation, rigidity and the ability to withstand compression is required  plastic lids and caps and the wadding used in such closures 35 www.Agrimoon.Com Food Packaging Technology  diaphragms on plastic and glass jars to provide product protection and tamper evidence plastic bands to provide external tamper evidence  pouring and dispensing devices to collate and group individual packs in multipacks, e.g. Hi-cone rings for cans of beer, trays for jars of sugar preserves etc.  plastic films used in cling, stretch and shrink wrapping  films used as labels for bottles and jars, as flat glued labels or heat shrinkable sleeves  components of coatings, adhesives and inks. 8.2. Types of plastic used in packaging 8.2.1 Polyethylene PE is structurally the simplest plastic and is made by addition polymerization of ethylene gas in a high temperature and pressure reactor. A range of low, medium and high density resins are produced, depending on the conditions (temperature, pressure and catalyst) of polymerization. Polyethylenes are readily heat sealable. They can be made into strong, tough films, with a good barrier to moisture and water vapor. They are not a particularly high barrier to oils and fats or gases such as carbon dioxide and oxygen compared with other plastics, although barrier properties increase with density. The heat resistance is lower than that of other plastics used in packaging, with a melting point of around 120°C, which increases as the density increases. LDPE and LLDPE can be used in blends with EVA to improve strength and heat sealing. There is a degree of overlap in application between LDPE and LLDPE, due to the fact that there are differences in both, as a result of the conditions of polymer manufacture and on- going product development. The thickness used for specific applications can vary, and this can also have commercial implications. MDPE or medium-density PE film is mechanically stronger than LDPE and therefore used in more demanding situations. LDPE is coextruded with MDPE to combine the good sealability of LDPE with the toughness and puncture resistance of MDPE, e.g. for the inner extrusion coating of sachets for dehydrated soup mixes. HDPE or high-density PE is the toughest grade and is extruded in the thinnest gauges. This film is used for boil-in-the-bag applications. To improve heat sealability, HDPE can be coextruded with LDPE to achieve peelable seals where the polymer layers can be made to separate easily at the interface of the co- extrusion. 8.2.2 Polypropylene (PP) PP is an addition polymer of propylene formed under heat and pressure using Zieger- Natta type catalysts to produce a linear polymer with protruding methyl (CH2) groups. The resultant polymer is a harder and denser resin than PE and more transparent in its natural form. The high melting point of PP (160°C) makes it suitable for applications where thermal resistance is needed. The surfaces of PP films are smooth and have good melting characteristics. PP films are relatively stiff. When cast, the film is glass clear and heat 36 www.Agrimoon.Com Food Packaging Technology sealable. It is used for presentation applications to enhance the appearance of the packed product. PP is chemically inert and resistant to most commonly found chemicals, both organic and inorganic. It is a barrier to water vapor and has oil and fat resistance. Aromatic and aliphatic hydrocarbons are, however, able to be dissolved in films and cause swelling and distortion. Many of the PP films are used in the form of laminations with other PP and PE films. This allows for the reverse-side printing of one surface, which is then buried inside the subsequent laminate. 8.2.3 Polyethylene terephthalate (PET) PET can be made into film by blowing or casting. It can be blow moulded, injection moulded, foamed, extrusion coated on paperboard and extruded as sheet for thermoforming. PET can be made into a biaxially oriented range of clear polyester films produced on essentially the same type of extrusion and Stenter-orienting equipment as OPP. PET melts at a much higher temperature than PP, typically 260°C, and due to the manufacturing conditions does not shrink below 180°C. This means that PET is ideal for high-temperature applications using steam sterilization, boiling-the-bag and for cooking or reheating in microwave or conventional radiant heat ovens. The film is also flexible in extremes of cold, down to −100°C. PET is a medium oxygen barrier on its own but becomes a high barrier to oxygen and water vapor when metalized with aluminum. This is used for vacuumised coffee and bag-in-box liquids, where it is laminated with EVA on both sides to produce highly effective seals. It is also used in snack food flexible packaging for products with high fat content requiring barriers to oxygen and ultra violet (UV) light. PET film is also used as the outer reverse-printed ply in retort pouches, providing strength and puncture resistance, where it is laminated with aluminium foil and either PP or HDPE. PET can be oxide coated with SiO2 to improve the barrier, whilst remaining transparent, retortable and microwaveable. PET is the fastest growing plastic for food packaging applications as a result of its use in all sizes of carbonated soft drinks and mineral water bottles which are produced by injection stretch blow moulding. PET bottles are also used for edible oils, as an alternative to PVC. 8.2.4 Ethylene vinyl acetate (EVA) EVA is a copolymer of ethylene with vinyl acetate. It is similar to PE in many respects, and it is used, blended with PE, in several ways. The properties of the blend depend on the proportion of the vinyl acetate component. Generally, as the VA component increases, sealing temperature decreases and impact strength, low temperature flexibility, stress resistance and clarity increase. EVA is also a major component of hot melt adhesives, frequently used in packaging machinery to erect and close packs, e.g. folding cartons and corrugated packaging. Modified EVAs are available for use as peelable coatings on lidding materials such as aluminum foil, OPP, OPET and paper. They enable heat sealing, resulting in controllable heat seal strength for easy, clean peeling. These coatings will seal to both flexible and rigid PE, PP, PET, PS and PVC containers. 8.2.5 Polyamide (PA) 37 www.Agrimoon.Com Food Packaging Technology Polyamides (PA) are commonly known as nylon. However, nylon is not a generic name; it is the brand name for a range of nylon products made by Dupont. They were initially used in textiles, but subsequently other important applications were developed including uses in packaging and engineering. Polyamide plastics are formed by a condensation reaction between a diamine and a diacid or a compound containing each functional group (amine). The different types of polyamide plastics are characterized by a number which relates to the number of carbon atoms in the originating monomer. PA resins can be used to make blown film, and they can be coextruded. PA can be blended with PE, PET, EVA and EVOH. It can be blow moulded to make bottles and jars which are glass clear, low in weight and have a good resistance to impact. PA film is used in retortable packaging in structures such as PA/aluminum foil/PP. The film is non- whitening in retort processing. PA is relatively expensive compared with, for example, PE, but as it has superior properties, it is effective in low thicknesses. 8.2.6 Polyvinyl chloride (PVC) PVC has excellent resistance to fat and oil. It is used in the form of blowmoulded bottles for vegetable oil and fruit drinks. It has good clarity. As a film, it is tough, with high elongation, though with relatively low tensile and tear strength. The moisture vapor transmission rate is relatively high, though adequate for the packaging of mineral water, fruit juice and fruit drinks in bottles. PVC softens, depending on its composition, at relatively low temperatures (80–95°C). PVC easily seals to itself with heat, but heat sealing with a hot wire has the disadvantage of producing Hcl gas. Most PVC films are produced by extrusion, using the bubble process. It can be oriented to produce film with a high degree of shrinkability. Up to 50% shrinkage is possible at quite low temperatures. The film releases the lowest energy of the commonly used plastic films when it is heat shrunk around products. It is plasticized, and the high stretch and cling make it suitable for overwrapping fresh produce, e.g. apples and meat in rigid trays using semi-automatic and manual methods. Unplasticised PVC (UPVC) has useful properties but is a hard, brittle material, and modification is necessary for it to be used successfully. Flexibility can be achieved by the inclusion of plasticizers, reduced surface friction with slip agents, various colors by the addition of pigments and improved thermal processing by the addition of stabilizing agents. 8.2.7 Polystyrene (PS) It is less well known as an oriented plastic film, though the film has interesting properties. It has high transparency (clarity). It is stiff, with a characteristic crinkle, suggesting freshness, and has a dead fold property. It has a low barrier to moisture vapor and common gases, making it suitable for packaging products, such as fresh produce, which need to breathe. PS is easily processed by foaming to produce a rigid lightweight material which has good impact protection and thermal insulation properties. 38 www.Agrimoon.Com Food Packaging Technology Lesson- 9 Metal 9.0. Introduction Two basic types of alloyed metals are used in food packaging i.e. steel and aluminum. Steel is used primarily to make rigid cans, whereas aluminum is used to make cans as well as thin aluminum foils and coatings. Nearly all steel used for cans was coated with a thin layer of tin to inhibit corrosion, and called as ―tin can‖. The reason for using tin was to protect the metal can from corrosion by the food. Tin is not completely resistant to corrosion, but its rate of reaction with many food materials is considerably slower than that of steel. The strength of the steel plate is another important consideration especially in larger cans that must withstand the pressure stresses of retorting, vacuum canning and other processes. Can strength is determined by the temper given the steel, the thickness of the plate, the size and the geometry of the can, and certain construction features such as horizontal ribbing to increase rigidity. This ribbing is known as beading. The user of cans will find it necessary to consult frequently with the manufacturer on specific applications, since metal containers like all other materials of packaging are undergoing constant change. Aluminum is light weight, resistant to atmospheric corrosion, and can be shaped or formed easily. However, aluminum has considerably less structural strength than steel at the same gauge thickness. This means that aluminum has limited use in cans such as those used with retorted foods. Aluminum works well in very thin beverages cans that contain internal pressure such as soda or beer. This internal pressure from CO2 gives rigidity to the can. Aluminum in contact with air forms an aluminum oxide film which is which is resistant to atmospheric corrosion. However, if the oxygen concentration is low, as it is within most foods containing cans, this aluminum oxide film gradually becomes depleted and the underlying aluminum metal is then no longer highly resistant to corrosion. (potter) 9.1 Metals used in packaging The metal materials used in food packaging are aluminum, tinplate and electrolytic chromium-coated steel (ECCS). Aluminum is used in the form of foil or rigid metal. 9.1.1. Aluminum Foil Aluminum foil is produced from aluminum ingots by a series of rolling operations down to a thickness in the range 0.15–0.008 mm. Most foil used in packaging contains not less than 99.0% aluminum, with traces of silicon, iron, copper and in some cases, chromium and zinc. Foil used in semi rigid containers also contains up to 1.5% manganese. After rolling, foil is annealed in an oven to control its ductility. This enables foils of different tempers to be produced from fully annealed (dead folding) to hard, rigid material. Foil is a bright, attractive material, tasteless, odorless and inert with respect to most food materials. For contact with acid or salty products, it is coated with nitrocellulose or some polymer material. It is mechanically weak, easily punctured, torn or abraded. Foil is used 39 www.Agrimoon.Com Food Packaging Technology as a component in laminates, together with polymer materials and, in some cases, paper. These laminates are formed into sachets or pillow packs on FFS equipment (see Section 9.3.6). Examples of foods packaged in this way include dried soups, sauce mixes, salad dressings and jams. Foil is included in laminates used for retortable pouches and rigid plastic containers for ready meals. It is also a component in cartons for UHT milk and fruit juices. 9.1.2. Tin 9.1.2.1. Tinplate Tinplate is the most common metal material used for food cans. It consists of a low- carbon, mild steel sheet or strip, 0.50–0.15 mm thick, coated on both sides with a layer of tin. This coating seldom exceeds 1% of the total thickness of the tinplate. The mechanical strength and fabrication characteristics of tinplate depend on the type of steel and its thickness. The minor constituents of steel are carbon, manganese, phosphorous, silicon, sulphur and copper. At least four types of steel, with different levels of these constituents, are used for food cans. The corrosion resistance and appearance of tinplate depend on the tin coating. 9.1.2.2. Tin coating The role of tin coating is an essential component of the can construction and plays an active role in determining shelf life. The most significant aspect of the role of the tin coating is that it protects the steel base-plate which is the structural component of the can. Without a coating of tin, the exposed iron would be attacked by the product and this would cause serious discoloration and off-flavors in the product and swelling of the cans; in extreme cases the iron could be perforated and the cans would lose their integrity. The second role of tin is that it provides a chemically reducing environment, any oxygen in the can at the time of sealing being rapidly consumed by the dissolution of tin. This minimizes product oxidation and prevents colour loss and flavor loss in certain products. 9.1.2.3 Tin toxicity High concentrations of tin in food irritate the gastrointestinal tract and may cause stomach upsets in some individuals, with symptoms which include nausea, vomiting, diarrhoea, abdominal cramps, abdominal bloating, fever and headache. Tin corrosion occurs 40 www.Agrimoon.Com Food Packaging Technology throughout the shelf life of the product. It is therefore imperative to take steps to reduce the rate of corrosion. Accelerating factors include heat, oxygen, nitrate, some chemical preservatives and dyes, and certain particularly aggressive food types (e.g. celery, rhubarb). A high vacuum level is one effective method of reducing the rate of tin pick-up in cans with un-lacquered components. 9.2. Electrolytic Chromium-Coated Steel (ECCS) Electrolytic chromium-coated steel (ECCS), sometimes described as tin free steel, is finding increasing use for food cans. It consists of low-carbon, mild CR or DR steel coated on both sides with a layer of metallic chromium and chromium sesqueoxide, applied electrolytically. ECCS is less resistant to corrosion than tinplate and is normally lacquered on both sides. It is more resistant to weak acids and sulphur staining than tinplate. Figure1: Structure of ECCS plate 9.3. Aluminum Alloy Hard-temper aluminum alloy, containing 1.5–5.0% magnesium, is used in food can manufacture. It is lighter but mechanically weaker than tinplate. It is manufactured in a similar manner to aluminum foil. It is less resistant to corrosion than tinplate and needs to be lacquered for most applications. A range of lacquers suitable for aluminum alloy is available, but the surface of the metal needs to be treated to improve lacquer adhesion. 9.4. Lead Lead was a problem with older, soldered cans but levels are now very low. However, some tinplate is contaminated with minimal amounts of lead. The manufacture of lead soldered cans may still be found in the developing world. 9.5. Lacquers The presence of lacquer or enamel very effectively limits dissolution of tin into the product, and so the use of lacquers is becoming increasingly common, even with those products which were previously packed in plain tinplate cans. There are several different types of lacquer in common use today. By far the most common type is the Epoxy Phenolic group, which are suitable for packing meat, fish, vegetable and fruit products. 41 www.Agrimoon.Com Food Packaging Technology These have largely replaced the oleoresinous group, which had a similar wide range of application. Some canners use cans lacquered with vinyl resins, which have the important quality of being free from any taste and odor, and are therefore particularly suitable for dry packs such as biscuits and powders, but also some drinks. White vinyl lacquers have been used where staining of the underlying metal caused by reaction with the product is a problem. Also, white vinyl lacquers have been used for marketing reasons in order to present a hygienic/clinical appearance and not the aesthetically undesirable corrosion patterns on tinplate. 42 www.Agrimoon.Com Food Packaging Technology Lesson- 10 Other packaging materials 10.1. Edible films Edible films and coatings formed from polysaccharides, proteins, lipids, resins, and/or waxes fall within the active packaging definition, since they can enhance the protective function, provide convenience, and minimize package environmental impact. Edible films placed or formed between components of a packaged food control transfer of moisture, oils, etc. over which the package has no control. Edible coatings or edible film pouches (as a primary package) work to complement the protective function of the nonedible (secondary) package. Such coatings and films can act as barriers to the external environment and maintain food integrity, thus reducing the amount of packaging required. Edible film pouches carrying premeasured amounts of ingredients can provide the convenience of placing pouch with ingredients into the food formulation. Edible coatin