Preservation: past, present and future.

Foods deteriorate in quality due to a wide range of reactions including some that are physical, some that are chemical, some enzymic and some microbiological. The various forms of spoilage and food poisoning caused by micro-organisms are preventable to a large degree by a number of preservation techniques, most of which act by preventing or slowing microbial growth. These include freezing, chilling, drying, curing, conserving, vacuum packing, modified atmosphere packing, acidifying, fermenting, and adding preservatives. In contrast, a smaller number of techniques act by inactivating micro-organisms, predominantly heating (pasteurization and sterilization). Complementary techniques restrict access of micro-organisms to food products, e.g. aseptic processing and packaging. New and 'emerging' preservation techniques include more that act by inactivation. They include the application of ionizing radiation, high hydrostatic pressure, high voltage electric discharges, high intensity light, ultrasonication in combination with heat and slightly raised pressure ('manothermosonication'), and the addition to foods of bacteriolytic enzymes, bacteriocins, and other naturally-occurring antimicrobials. Major trends, reacting to consumers' needs, are towards the use of procedures that deliver food products that are less 'heavily' preserved, higher quality, more convenient, more 'natural', freer from additives, nutritionally healthier, and still with high assurance of microbiological safety.