Electromagnetics, heat transfer, and thermokinetics in microwave sterilization

Sterilization of solid foods using microwave power was studied using numeri cal modeling and specialized experimental verification. Maxwell's equations and the heat conduction equation were coupled using two separate finite-el ement programs and specially written modules to couple the programs. Spatia l distributions of thermal-time, representing sterilization, were calculate d fi-om time-temperature history and first-order kinetics. Experimentally, concentrations of marker compounds formed during heating were measured and taken as indices of thermal-time. Experimental data oil marker formation co mbined with numerical calculations provide an accurate and comprehensive pi cture of the sterilization process and represent a major step in establishi ng the efficacy, of microwave sterilization processing. Unlike conventional sterilization, heating patterns can change qualitatively with geometry (sh ape and size) and properties (composition) of the food material, but optima l heating is possible by choosing suitable combinations of these factors. C ombined with marker yield measurements, the numerical model can give compre hensive descriptions of the spatial time-temperature history, and thus can be used to verify, the sterilization process.