Thermal Processing

The word "thermal" applies to heat-related processes. Heating food is an active way to preserve it, as the vast majority of harmful pathogens are killed near the boiling point of water at temperatures. Heating foods in this respect is a form of food preservation comparable to that of freezing, but in its efficacy far superior to it. A preliminary step in many other types of food preservation, especially forms that use packaging, is to heat the food to temperatures that are high enough to kill pathogens. In many cases, before they are packaged and processed, foods are actually cooked. Cooking is not sufficient or necessary in other situations.

Pasteurization is the most common example of this latter case. The French bacteriologist Louis Pasteur discovered during the 1860s that pathogens can be destroyed in food by heating those foods to a certain minimum temperature. The method is particularly appealing to preserve milk as it is not a practical approach to preserve milk by boiling. Conventional pasteurization methods required milk to be heated to a temperature between 145 and 149 ° F (63 and 65 ° C) for approximately 30 minutes and then cooled to room temperature.

"Canning" is the term used to describe industrial sterilization and is regarded as a highly intense method of heating. It therefore needs a lowest temperature of 121 ° C for up to 15 minutes. The process takes place in the correct canister after the packaging. Usually, items that are commercially sterilized can last for two or more years and therefore have a long shelf life.