Retortable plastics

Attempts have been made to perform thermal retorting ia a gas barrier flexible pouch or tray. The retort pouch, under development for many years, has a higher surface-to-volume ratio than a can and employs a heat seal rather than a mechanical closure. Similarly, plastic retort trays have higher surface-to-volume ratios and are usually heat seal closed. Plastic cans iatended for microwave reheating are composed of bodies fabricated from multilayer plastic including a high oxygen barrier material, plus double-seam aluminum closures. 

Retortable plastics. Retortable plastics packs are directed at two markets competition with tinplate or aluminium cans and glass jars in parts of the shelf-stable foods market where the foods can be reheated in the bowl or tray and replacement of chilled or frozen foods in the ready-to-eat (single serve) mode in a shelf-stable format. The aim is to provide food subjected to a somewhat shorter heat process than with cans, due to the flatter geometry of the packs and provision for microwave reheating for convenience in the home, institution or vending machine. 

Until the end of World War II, coal tar was the main source of these aromatic chemicals. However, the enormously increased demands by the rapidly expanding plastics and synthetic-fiber industries have greatly outstripped the potential supply from coal carbonization. This situation was exacerbated by the cessation of the manufacture in Europe of town gas from coal in the eady 1970s, a process carried out preponderantly in the continuous vertical retorts (CVRs), which has led to production from petroleum. Over 90% of the world production of aromatic chemicals in the 1990s is derived from the petrochemical industry, whereas coal tar is chiefly a source of anticorrosion coatings, wood preservatives, feedstocks for carbon-black manufacture, and binders for road surfacings and electrodes. 

Process particulate pickup may significantly increase the risk of boiler foaming. This kind of problem happens in the crossover of hot to cold water during manufacturing processes, as in rubber tire factories, food can cookers and retorts, plastic injection molding, and the like). 

Plastic film photography supports, 19 197 Plastic films, properties of, 17 835t Plastic flow, 8 727 Plastic food packaging, 18 40-51 retortable, 18 49... 

The benefit of these closures is that they have two forms of tamper evidence a vacuum-indicating button and a plastic tamper-evident band. They are ideal for hot-fill, cold-fill and retorted processes, and generally are available in the smaller 40-51 mm size range. 

The rubber or plastic outlet tube should be depression-free and lead via an adapter into the receiver flask (see below) which must be sited in the fume cupboard, and it is advised that this delivery tube be additionally supported by means of a retort stand and clamp. This latter precaution is necessary since the initial force of ammonia release may cause it to flex with considerable thrust which may lead to apparatus damage. 

Family of plastics that can be used in hot fill and retort packaging applications that provide clarity and heat resistance. 

Barrier Properties of Ethylene—Vinyl Alcohol Copolymer in Retorted Plastic Food Containers... 

In the early days of storage, the expected sensitivity of EVOH permeability to moisture plasticization Is seen. Figure 1 shows that the permeability immediately following a 100 minute retort at 240°F is about 25 times higher than the permeability when the container is not retorted. As retort time increases, the increased moisture ingress into the EVOH layer causes higher permeability. 

Tsai, B.C. andB. Jenkins, "Effect of Retorting on the Barrier Properties of EVOH", Plastic Film Sheet 1988, 4., p 63. 

American Can s Omni retortable plastic can marks a major development in food packaging. The five layer can, used by Hormel, Del Monte, and Campbell Soup Company, consists of polyolefin structural layers, adhesive layers incorporating desiccants, and ethylene vinyl alcohol (EVOH) polymer as the barrier layer. 

The market for plastic cookware that can be used in the fi-eezer and microwave is set for a big expansion. Most cookware is made up of fiberglass reinforced thermoset resins. High-barrier multilayer containers that have gained popularity in the market are heat retortable, microwaveable, and provide a shelf life of up to two years without refrigeration for a variety of convenience foods. Liquid crystal polymers have also been used to make cookware as they are transparent to microwave, offer high heat resistance, and give an excellent finish. 

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