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Thermal preservation requires accurate estimation of lethality for design of a microbiologically safe thermal preservation process and alternatives to first-order model of death kinetics of microorganisms are proposed. The Monte Carlo simulation was used to include variability in input parameters and the results show that for the same percent variability in kinetic parameters, uncertainty in the final log reduction was lower for Weibull kinetic parameters.

Thermal stresses were studied in freezing of biomaterials containing significant amounts of water. An apparent specific heat formulation of the energy equation and a viscoelastic model for the mechanics problem were used to analyze the transient axi-symmetric freezing of a long cylinder. Viscoelastic properties were measured in an Instron machine. Results show that, before phase change occurs at any location, both radial and circumferential stresses are tensile and keep increasing until phase change begins. The maximum principal tensile stress during phase change increases with a decrease in boundary temperature (faster cooling). This is consistent with experimentally observed fractures at a lower boundary temperature. Large volumetric expansion during water to ice transformation was shown to be the primary contributor to large stress development. For very rapid freezing, relaxation may not be significant, and an elastic model may be sufficient.

Food scientists can utilize computer-aided engineering (CAE) to minimize food product and process development cycles. The technology supports concurrent design and analysis. It allows scientists to view results simultaneously with optimization processes. CAE does not only reduce product development cycles, it also minimizes the building of physical prototypes while simplifying assumptions related to computations.

Several optimization processes for reducing the food quality-degradation problems involved in the use of microwave heating are formulated. Tests are conducted wherein the characteristics of both microwave and conventional process are compared using an energy equation with a heat-generation term. The alternating-direction implicit finite difference method is then applied to obtain the effects of various processing parameters, such as spatial variation, on the food quality. Results show that a more uniform microwave heating could reduce the thermal degradation of the food quality.