Convenience foods are tinned or frozen foods which are easy to prepare and can be used at any time. Canning is the most common method of food preparation in industrialised countries. In this process, foods that have been sealed in airtight containers called cans, tins, or jars are heated to destroy micro-organisms that may cause spoilage. Canning plants produce a wide variety canned foods, including fruit, vegetables, fish, meat, poultry and soups.
Before any food is canned, it is throughtly cleaned. Many foods, such as fruits and vegetables, are cut, sliced or peeled before canning. Freezing removes heat from food throught the use og low temperatures, Freezing slows the growth of micro-organisms and stops the breakdown of nutrients. Because most foods contain large amounts of water, they freeze solidly at 0 degree to -4 degree C.
Vegetables are among the amin foods preserved by freezing. Before they are frozen, vegetables are first blanced. Blancing prevents enzymes, which are not killed during freezing, from changing the flavour of vegetables. Other foods preserved by freezing include meat, fish, poultry and juices . Before freezing, food may be cleaned, peeled or prepared in other way. Some foods, such as those used for frozen oven ready meals, are cooked before freezing.