Thermal processing is a very common method of food preservation. The thermal treatment consists of applying heat to a food product at a specific temperature for a determined interval of time. The process time is calculated to achieve sufficient microbial destruction to comply with public health standards and prevent spoilage of the food product. The thermal processing kinetics can be defined in terms of D, z and F values (Teixeira, 1992; Singh and Heldman, 1993; Hendrickx et al., 1995). D value is the time in minutes required to decrease a quality attribute by 90percent at a constant temperature. The z value is the temperature increase necessary to reduce the D value by 90percent. The F value is the time required to achieve a stated reduction in a population of microorganisms or spores. This time is usually expressed as a multiple of the D value. Many thermal processes have been standardized, and published recommendations for specific conditions are available (National Canners Association, 1968). Even with reliable thermal processing schedules and equipment, though, there is a need to determine process compliance to ensure food safety.
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