Food Packaging

Glass, woven, natural fiber, and ceramic containers have been used to store food since antiquity. However, the invention of tin-plated steel containers (ca 1800) provided the food industry with its first functional and disposable packaging system. Advances in metal container manufacturing continue to maintain the status of the cylindrical can as the primary package for heat-processed, shelf-stable foods and beverages. Notable developments include substitution of electrolytic tin plating for hot dipping, new organic linings to greatly reduce the need for tin, reduced steel thickness, and improved steel composition for better strength and corrosion resistance. Developments in coating technology have resulted in the availability of two-piece drawn aluminum and steel containers and of numerous easy-open systems. New glass containers have increased strength and have continued to reduce package weight and cost.

Rigid glass or metal containers have a major processing advantage: they can be filled and sealed at speeds in excess of 1000/min. Thus the relatively higher container cost can be recovered to some degree by higher production rates. Their rigidity (ie, sturdiness) facilitates stacking and handling during distribution and storage.

Paper, plastics, and aluminum have provided the food industry with container material that can be tailored to specific barrier needs. Ease of forming, sealing, opening, and decoration; strength; and low weight have made them preferred materials for refrigerated, dry, and frozen products.

Resistance to thermal treatment and desired barrier and mechanical qualities are obtained by laminating or coextruding appropriate combinations of paper, aluminum foil, and plastic. Lamination and coextrusion seal transparent packages against moisture and gas permeation and strengthen the packaging.

Pouches formed by heat-sealing paper-foil-plastic laminates on three sides, filling, and then heat-sealing the fourth side have found extensive use with moisture- and oxygen-sensitive dry foods as well as with high-moisture thermally processed foods. Pouches capable of withstanding saturated steam or steam-air mixtures at 121°C for several hours are finding greater use as substitutes for metal and glass containers. The advantage of pouches for heat sterilization is their slab rather than cylindrical shape. Their thinner cross section allows a shorter heat-processing time than cylindrical containers of the same capacity. Mechanical advances in forming, filling, sealing, and handling pouches will result in continued substitution of laminates for rigid metal and glass containers.

Plastics and plastic-coated papers are widely used for beverages, including carbonated drinks. Several aseptic systems are marketed for bulk packing of liquids in multiliter plastic bags.

Semirigid containers are also gaining increased acceptance, particularly as replacements for the #10 can (2.72 kg or 96 oz). Initial developments have produced a lightweight drawn-metal container measuring 24 x 30 x 6 cm with a double-seamed top. The thickness of this container (6 cm) is such that during heat sterilization, heat travels only 3 cm by conduction versus about 8 cm in the conventional #10 can. Shorter heat treatments allow the preservation of a greater variety of specialty products. The half-steam-table size eliminates cleaning of pans, because the opened unit serves as a serving tray. Other semirigid systems have been developed to replace the steel can for single-portion service. These containers generally use a heat-sealed or glued paper-foil-plastic laminated closure.

Aerosol containers have played a specialized role in the food industry as dispensers for such foods as whipped toppings (using nitrous oxide as a propellant), cake frosting, and barbecue sauces. Special filling techniques and product formulations are required because the aerosol package cannot be heat sterilized once it has been sealed.

Packaging forms an integral part of most food processing. For this reason, studies of storage conditions over a range of temperatures, relative humidities, and handling conditions must be made to determine the suitability of a package. Packaging in contact with foods must be tested for migration of packaging components under actual conditions of use, and pickup of off-flavor must be evaluated on a product-by-product basis. Because of potential migration of packaging materials into foods, current food and drug regulations should be consulted prior to marketing foods packaged in nonstandard materials.

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