Heat transfer is arguably the most important transport process in the food industry, since processing of most foods requires either an increase or a decrease in temperature. Thermal processing, or heating to destroy undesirable microorganisms, is one of the main techniques a food technologist utilizes to ensure safety of the food supply. Sterilization and pasteurization require that a food be heated to a certain temperature and held there for sufficient time to destroy microorganisms before being cooled again. Both the heating and cooling steps require an understanding of heat-transfer principles. There are numerous other examples of heat transfer in the food industry, from baking a food in an oven, to solidification of chocolate in a cooling tunnel. Nearly every food processing system utilizes heat transfer in some form or another. Thus, knowledge of the principles of heat transfer is critical for the food technologist. Furthermore, using the principles of heat transfer together with enthalpy balances provides a powerful tool for the food technologist to solve complex food-processing problems.