ABSTRACT
Understanding the way in which populations of microorganisms decrease in response to heat is fundamental to the engineering design of thermal inactivation processes important in the food, pharmaceutical, and bioprocess industries. Thermal inactivation of a microorganism implies a loss of the ability to grow and reproduce, and not a physical destruction or fragmentation. A practical working deƒnition however is “to reduce the number of viable contaminants to a desired level following thermal treatment.” This is referred to as the sterility requirement. Thermal sterilization is widely used because of good reliability and economy. Nucleic acids, structural proteins, and enzymes of microorganisms are denaturized and hence inactivated by moist heat treatment. Thermal sterilization can be operated either as a batch or a continuous process. Continuous thermal processes, which operate at steady state, are widely preferred to the batch process because greater control of the process temperature and exposure time is possible. The continuous process provides improved product quality and is less laborious than a batch process. Because of the risks associated with error to public health, heat treatment operations must be conservative.
