There are two main temperature categories employed in thermal processing: Pasteurization and Sterilization. The basic purpose for the Thermal Processing of foods is to reduce or destroy microbial activity, reduce or destroy enzyme activity and to produce physical or chemical changes to make the food meet a certain quality standard. E.g. gelatinization of starch and denaturation of proteins to produce edible food. There are a number of types of heat processing employed by the food industry.