Thermal Processing of Food

Abstract

Precise evaluation of the thermal resistance of microorganisms in food processing is critical for the design of thermal processes. The reduction in microbial population during thermal processing follows first-order kinetics. The D-value, z-value, and F-value are the biological indicators that must be configured to meet requirements concerning survival of microbial spores in processed foods. The D-value provides the time taken to achieve a one-log reduction in the spore population at a certain temperature, while the z-value expresses an organism’s tolerance to varying temperatures. In other words, the z-value is the inverse of the slope that emerges from the D-value logarithm plot versus the temperature. The thermal death time, referred to as F-value, is defined as the time needed to cause a specific reduction in a given microbial population and is usually expressed as a multiple of D. The kinetic model of microorganism thermal death also refers to the thermal inactivation of enzymes. The kinetic model of thermal death of microorganisms is also applicable to the thermal destruction of phytochemical compounds and thermal inactivation of enzymes in food products.