THERMAL CONDUCTIVITY OF SELECTED FOODS AT HIGH-PRESSURE PROCESSING CONDITIONS

Thermal conductivity data for foods under high-pressure processing (HPP) conditions is necessary for modeling the associated heat transfer processes, such as HP sterilization, pressure shift freezing, etc. Available data in the literature are scarce because of the difficulties associated with property measurements. In this study, a thermal conductivity probe based on line heat source theory was used under HPP conditions. The probe was calibrated using 1.5% agar gel in the HP range of 0.1 to 400 MPa and temperature range of 25 degrees C to 55 degrees C. No clear pressure, temperature, or power supply dependency trend of the calibration factor was observed. A general calibration factor (1.01) was obtained by linear regression analysis between all measured values and reference values of water at different HPP conditions. Thermal conductivities of selected food materials (tofu, wheat flour dough, and pork) were then measured under similar HPP conditions and corrected using the calibration factor. The evaluated thermal conductivity of food materials ranged from 0.40 to 0.79 W m(-1) degrees C-1 and increased with increasing pressure and temperature. A prediction model was developed to give a good fit (R-2 >= 0.91) for the thermal conductivity of each food material with pressure and temperature.