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224 FOOD PACKAGING TECHNOLOGY Table 7.3 Examples of suitability of various films for packing the products named Product Fresh bread Long life bread Snacks/crisps (chips) Biscuits Nuts Cooked meat Frozen food LDPE OPP OPP (metallised) OPP (coated) Laminate (no Al) Laminate (+ Al) Package type *** 0 *** 0 0 * 0 *(MAP) 0 **(MAP) 0 **(MAP) HFF HFF 0 * *** *** ** *** VFF 0 0 0 ** 0 0 0 * ** **(MAP) * * *** *(MAP) ** 0 ** **(MAP) **(MAP) *** *** ***(MAP) ***(MAP) *** HFF VFF Pouch Various 0 = Not suitable, * = short life, ** = medium life, *** = long life, MAP = modified atmosphere pack. gas permeability, optical properties, packing machine performance and heat sealability. The commercial consideration of cost must also be considered. Run lengths and lead times are also important. It is not unknown for there to be run length cost differences, where at one point a particular solution is cost effective relative to an alternative solution and for the position to be reversed at a different run length. 7.11 7.11.1 Retort pouch Packaging innovation The retort pouch is discussed here as a demonstration, case study, of the integrated approach involving packaging materials, their conversion, forming, filling and sealing together with the processing and machinery which is necessary to establish any new form of product/packaging presentation. The retort pouch is a rectangular, flexible, laminated plastic, four-side hermetically sealed pouch in which food is thermally processed. It is a lightweight, high-quality, durable, convenient and shelf stable pack. Foods packed and processed in retort pouches are in successful commercial use for a wide variety of foodstuffs in several countries, particularly Japan. They were originally developed in the 1950s and 1960s in America through research and encouragement from the US Army. The materials from which retort pouches are made are either aluminium foil bearing/plastic laminates or foil-free plastic laminate films. These must be inert, heat sealable, dimensionally stable and heat resistant to at least 121Â°C for typical process times. They should have low oxygen and water vapour permeability, be physically strong and have good ageing properties (Table 7.4).