Thermal conductivity of selected liquid foods at elevated pressures up to 700 MPa

Thermal conductivity (k) of selected liquid foods during high- pressure processing (HPP) was studied using a line heat source probe. The probe was calibrated using distilled water and probe specific calibration factors were developed by comparing experimental data against published data from National Institute of Standards and Technology (NIST) for water. k of commercially available apple juice, canola oil, clarified butter, honey and high fructose corn syrup (HFCS) were then determined using a custom made high pressure experimental setup for various pressures (0.1, 100, 300, 500 and 700 MPa) at 25 °C. Results indicated that material k increased linearly with increasing pressures up to 700 MPa. Water and water-like substances (apple juice) were found to have the highest k values (up to 0.82 W/m °C at 700 MPa), while fatty foods such as canola oil and clarified butter had the lowest (0.29–0.4 W/m °C, respectively at 700 MPa) values. Honey and HFCS had intermediate values. The combined uncertainty (including Type A and Type B) in the measurement of k values of various liquid foods ranged from 0.6% (canola oil) to 3.8% (HFCS).