tailieunhanh - Preservation of fish and meat - Part 8

8 Canning General information First, some general information about canning of fish and meat will be given. This covers the advantages and disadvantages of the process, packaging materials and materials needed. After this general introduction, the following will be described: | 8 Canning General information First some general information about canning of fish and meat will be given. This covers the advantages and disadvantages of the process packaging materials and materials needed. After this general introduction the following will be described preparation of fish and meat processing techniques and storage of the product. A lot of canning equipment is manufactured in the . Therefore pressures and temperatures will be given both in metric and American measuring units . pounds inch2 and degrees Fahrenheit . Principle and limitations The canning process involves placing foods in cans or jars and heating them to a temperature that destroys micro-organisms that could be a health hazard or cause the food to spoil. Canning also inactivates enzymes that could cause the food to spoil. As the cans or jars are sealed hermetically re-contamination from outside is prevented. In general canned products can be stored for a long time without refrigeration. Chemical quality loss in taste colour and amount of certain essential nutrients will slowly continue though. Not all products can be heated in the same way. The amount of time and the temperature needed depends on the number and kinds of micro-organisms and the form active cells or spores in which they are present water content of the product acidity of the product presence of salt and or other inhibitors of bacterial growth fat content of the product shape and size of the tin can or glass jar storage temperature 64 Preservation of fish and meat In fish and meat the number of micro-organisms initially present may be large the internal water content is high and the pH is close to neutral. It is therefore difficult to kill all micro-organisms present and to get a safe product. The only safe way to sterilize low acid products such as fish and meat is by prolonged heating in a pressure canner or sterilizer in which temperatures higher than 100 C 212 0F can be reached. The main reason pressure .