Edible Films and Packaging Materials PDF

To produce edible films, the edible solutions are then casted on a tray, dried and detached. Coatings on the other hand are commonly used as dipping or spray solutions after which in both cases, drying is applied (following figure). Materials used as edible films or coatings can be diverse. For exa...

To produce edible films, the edible solutions are then casted on a tray, dried and detached. Coatings on the other hand are commonly used as dipping or spray solutions after which in both cases, drying is applied (following figure). Materials used as edible films or coatings can be diverse. For example, polysaccharides such as cellulose, chitosan, starch, pectin and alginate can be used, having different effects. Cellulose is a widely used material for this kind of purpose, being tasteless, odorless, transparent, and having high oxygen, carbon dioxide and lipid 80 barrier properties. However, it has low resistance against water vapor transmission. Chitosan is a compound that is obtained from the outer skeletons of shellfish. It is transparent, hard but flexible and has good oxygen barrier and mechanical properties. Starch is also known to be transparent, odorless, tasteless, water soluble and has good oxygen and carbon dioxide barriers but it also has poor water vapor barrier properties. Proteins can also be used to produce edible films and coatings. These include for example collagen and gelatin which have good transparency, mechanical and barrier properties. Wheat gluten is also used, being transparent, mechanically strong, and insoluble in water. Whey protein can be used to create dense and strong films which have good oxygen and water vapor barrier properties. Finally, lipids such as waxes and paraffins give good gas and moisture barriers. 81 2. bioplastics/biodegradable Alternative packaging solutions such as bioplastics/biodegradable materials and edible films/coatings, may be considered as innovative application of food packaging since they are usually not included in conventional packaging systems. Bioplastics are a type of packaging materials which consist of polymers produced from natural or renewable resources. These include for example renewable biomass sources such as sugarcane, corn or other forms of cellulose or the use of microbes such as yeast. For example, one commonly used biobased and biodegradable polymer is polylactic acid which is primarily made from renewable resources such as corn by the fermentation of starch and condensation of lactic acid. In instance, it has been showed that when packaging meat in polylactic acid based packaging with needed modified atmosphere environment, no significant differences with conventional plastic and MAP were evaluated in 82 the sensory attributes, meat color or total bacteria count over extended storage times. The aim of using bioplastic materials is to limit the use of fossil fuels and to enhance the protection of the environment. Bioplastics are always from natural or renewable resources, but their end-of-life scenarios could be different. For example, under the right conditions, they can be biodegradable or even compostable. The PE, PET and PA can also be produced from bio-based polymers, although being biobased, they can be both biodegradable and non- biodegradable. Bioplastics such as polylactic acid (PLA), polyhydroxyalkanoate (PHA), polybutylene succinate (PBS) and starch blends are possible to biodegrade under right conditions. 3. Laminates Packages made of polymer films are not absolute barriers against the transfer of water and O2 through the package, although they may be excellent barriers against microorganisms and dirt. 83 Various flexible materials (papers, plastic films, thin metal foils) differ with respect to water vapor transmission, oxygen permeability, light transmission, pinhole and crease hole sensitivity and so on. Multilayers or laminates of these materials that combine the best features of each can be used to produce packaging materials with combined properties such as the strength of paper, heat seal ability of plastics, and barrier properties of aluminum foils. Such structured plastic films may be complete in themselves or be further bonded to papers or metal foils to produce more complex laminates. 4. Cloth materials Jute and cotton are woven materials which have been used for packaging foods. Sacks made of jute are used, to a limited extent, for fresh fruit and vegetables, grains and dried legumes. However, multiwall paper sacks and plastic sacks have largely replaced them for such products. Cotton bags have been used in the past for flour, sugar, salt and similar products. Again, paper and plastic bags are now mainly used for these foods. Cotton scrims are used to pack fresh meat. 5. Wooden Containers Outer wooden containers are used when a high degree of mechanical protection is required during storage and transport. They take the form of crates and cases. Wooden barrels are used for liquid products. The role of crates has largely been replaced by shipping containers. Open cases find limited use for fish, fruits and vegetables, although plastic cases are now widely used. 84 The wood used in cheese barrels, or cheese aging shelves, is often hardwood, such as oak, maple, or beech. These types of wood are chosen for their durability and the subtle influence they can have on the cheese’s flavor as it ages. 6. Composite Containers So called composite containers usually consist of cylindrical bodies made of paperboard or fiberboard with metal or plastic ends. Where good barrier properties are required, coated or laminated board may be used for the body or aluminum foil may be incorporated into it. Small containers, less than 200 mm in diameter, are referred to as tubes or cans and are used for foods such as salt, pepper, spices, custard powders, chocolate beverages and frozen fruit juices. 85 Larger containers, known as fiberboard drums, are used as alternatives to paper or plastic sacks or metal drums for products such as milk powder, emulsifying agents and cooking fats. 86  Recommendations of materials for different food products As described previously, various food products have different needs regarding quality and safety. One way to ensure high quality food in the market, is packaging which meets the needs of shelf-life and enables the containment, communication and convenience along the supply chain. Cereals are usually packaged in bags or boxes, made of plastic and/or paper/board. Cereal products, like breakfast cereals for example, are sensitive to moisture gain and therefore need a good moisture barrier to provide taste and freshness of the product. For this, HDPE polymers are typically used. When the package requires aroma or taste barrier, PA or Ethylene vinyl alcohol (EVOH) polymers are often used. Snack foods are often high in fat content and therefore require a package that provides an oxygen barrier. In addition, they also need moisture barrier to avoid moisture gain and light barriers. To avoid the package contacting with oil, grease resistance materials are also needed. Keeping in mind these requirements, fatty snack foods like potato chips for example can be packaged in barrier films containing foil, a metallized polymer film or a 87 barrier polymer like Ethylene vinyl alcohol (EVOH) or polyvinylidene dichloride (PVDC). For bakery products, moisture barrier is normally the critical property. For this case, polymers like LDPE, LLDPE, HDPE or PP can be used. The bags are usually closed either with a strip of adhesive tape or a plastic clip to reduce moisture loss. For sealability and optical properties, Ethylene-vinyl Acetate (EVA) is often used. Applications which require aroma and taste barriers (like cake mixes for example) are packaged in films with PA layer. For bread bags, a combination of LLDPE and LDPE can be used, where the LLDPE allows to make the package thinner (down gauging) and the LDPE provides good optics and Printability. Confectionery products include wide range of candies, biscuits, chocolates, gums, toffees, coatings, etc, with different barrier needs, including oxygen, moisture, and light. Chocolates can be packaged in aluminum and LDPE laminates as well as primary packaging along with paper or cardboard as secondary. Next to that, one of the most common used material for chocolate packaging is polypropylene PP. Hard candies, gum and caramels are usually wrapped/packaged individually and bagged in an overwrap package, using PE or PP based solutions. 88 Meat, poultry and fish packaging requires a package that provides high oxygen, moisture, odor and grease barrier protection. There are different ways to package flesh foods like these. For example, shrink bag method involves placing the meat into heat shrinkable barrier bag, which typically consists of Ethylene-vinyl acetate (EVA), polyvinylidene dichloride (PVDC) and/or PA. The bag is then heat shrunk by placing it in the water at 90°C. After shrinking, the bag holds closely to the meat and produces a tight vacuum pack. Another technique is the usage of thermoformed plastic bag, which is put into an enclosed chamber and evacuated. These bags usually consist of materials which include PET as the outside layer to provide strength, PA as the middle layer to provide good oxygen barrier and inner layers of LDPE or EVA copolymers which are good moisture barriers and can be easily heat sealed. The materials used for thermoforming are laminates of PA, PET or PVC and heat-sealing layers are LDPE or EVA copolymer. 89 Cheeses are categorised in the wide range of attributes and therefore have different needs regarding packaging. Cheeses can be defined with texture as very hard and hard, semisoft, and soft, fresh and processed cheeses. Very hard cheeses are ripened by bacteria and are characterized by a moisture content 20-25%. These products are usually Parmesan, Romano, and Grana. Hard cheeses are also ripened by bacteria and have moisture content of 30- 39%. Semi hard cheeses possess a moisture content of 40%–49%. Cheeses in these classes include Edam, Gouda, Cheshire, Gloucester, Derby, Leicester, Emmental, Gruyere, Provolone, Mozzarella and Kasseri. Since some cheeses age over time during storage, they need applicable packaging materials for these processes. Rindless cheese may be defined as cheese that has been ripened under a plastic film that allows little or no evaporation into the atmosphere to occur. These materials are usually combination of PET, LDPE and PA. 90 When oxygen barrier is required to prevent mold growth, Ethylene vinyl alcohol (EVOH) or polyvinylidene dichloride (PVDC) is typically used. 91