Thermal conductivity of selected solid foods under high pressure

Abstract

The objective of this study was to determine k of selected solid foods under combined pressure-thermal treatment. A custom-made line heat source probe was used as the k sensor. k sensor was calibrated with distilled water under pressure by comparing the experimental data against NIST reference data. k of carrots, cheddar cheese, guacamole and pork tenderloin were determined at 100 MPa increments up to 700 MPa at 25, 50 and 75˚C from the linear portion of logarithm of time versus temperature rise plot. k of chicken separable fat and chicken breast were also determined to determine the effect of combined pressure-thermal treatment on products varying in their fat content. Thermal profiles and uncertainty analysis were discussed. Probe calibration results showed good agreement with NIST data and the probe specific calibration factors were expressed as second order polynomials (R2>0.90). k values of all the tested samples were found to increase linearly with increase in pressure and temperature. k of carrot samples (88% MC; 0.58-0.79 W/m˚C at 25˚C; 0.63-0.84 W/m˚C at 50˚C) and were found to be close to that of water. Cheddar cheese (14% fat) and guacamole (5% fat) had lower k values than carrot samples at the tested conditions. Experiments with meat samples showed the effect of fat and moisture content on k under pressure. Knowledge on k of solid foods under pressure will help the food processors and regulators in evaluating the process uniformity of pressure treated products and further facilitate the development of relevant mathematical models.