Evaluation and comparison of thermal conductivity of food materials at high pressure

Thermal conductivity of foods at high pressure (HP) is important for understanding the thermal response of food products during HP processing. Available information is still very limited. In this study, a line heat source (LHS) probe was installed in a HP vessel to evaluate pressure-dependent thermal conductivity of food and related materials. The probe was calibrated using agar gel (2%, w/w), resulting in an excellent linear agreement between measured values and reference data of pure water. Experiments were conducted to determine thermal conductivity of several materials at pressures up to 350 MPa and initial temperatures of 5 and 25 °C. At given temperature and pressure, thermal conductivity depended on the nature of test samples and ranked in the decreasing order: water > fresh potato > Tylose > chicken breast > salmon fillet > cheddar cheese. Thermal conductivity was sensitive to both pressure and temperature, increasing with both. Polynomial regression model was found to give a good fit for thermal conductivity as a function of pressure both at 5 or 25 °C. Results from this study were generally comparable to available published values thereby indicating the usefulness of the experimental approach for thermal conductivity data gathering. © 2008 The Institution of Chemical Engineers.