Food Preservation.

... Food Preservation a) Canning The idea of canning is that it destroys any micro-organisms and their spores by applying heat. This is achieved by sterilising food within airtight containers to prevent re-contamination. The basic stages of canning are: * Filling the cans with product * Sealing the cans * Washing the cans * Sterilising the cans * Cooling the cans Food products that have been canned have very long shelf life and are stored at room temperature. b) Freezing Freezing is based on two ideas. Firstly, very low temperatures which inhibit growth of micro-organisms and reduce enzyme and chemical activity, and secondly the formation of ice crystals which draw available water away from food, therefore preventing the growth of micro-organisms. In a household environment, food is frozen by placing it in a freezer and allowing heat transfer to occur by conduction. This process can take several hours, depending on the type of food being frozen.

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