<P> Pasteurization is a process for preservation of liquid food . It was originally applied to combat the souring of young local wines . Today, the process is mainly applied to dairy products . In this method, milk is heated at about 70 ° C (158 ° F) for 15--30 seconds to kill the bacteria present in it and cooling it quickly to 10 ° C (50 ° F) to prevent the remaining bacteria from growing . The milk is then stored in sterilized bottles or pouches in cold places . This method was invented by Louis Pasteur, a French chemist, in 1862 . </P> <P> Vacuum - packing stores food in a vacuum environment, usually in an air - tight bag or bottle . The vacuum environment strips bacteria of oxygen needed for survival . Vacuum - packing is commonly used for storing nuts to reduce loss of flavor from oxidization . A major drawback to vacuum packaging, at the consumer level, is that vacuum sealing can deform contents and rob certain foods, such as cheese, of its flavor . </P> <P> Preservative food additives can be antimicrobial--which inhibit the growth of bacteria or fungi, including mold--or antioxidant, such as oxygen absorbers, which inhibit the oxidation of food constituents . Common antimicrobial preservatives include calcium propionate, sodium nitrate, sodium nitrite, sulfites (sulfur dioxide, sodium bisulfite, potassium hydrogen sulfite, etc .), and EDTA . Antioxidants include butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT). Other preservatives include formaldehyde (usually in solution), glutaraldehyde (insecticide), ethanol, and methylchloroisothiazolinone . </P> <P> Irradiation of food is the exposure of food to ionizing radiation . The two types of ionizing radiation used are beta particles (high - energy electrons) and gamma rays (emitted from radioactive sources such as cobalt - 60 or cesium - 137). Treatment effects include killing bacteria, molds, and insect pests, reducing the ripening and spoiling of fruits, and at higher doses inducing sterility . The technology may be compared to pasteurization; it is sometimes called "cold pasteurization", as the product is not heated . </P>

What preserved meat is an example of the earliest form of food preparation