High-pressure differential scanning calorimetry: Comparison of pressure-dependent phase transition in food materials

Abstract

High-pressure (HP) differential scanning calorimetry (DSC) was used to evaluate and compare the pressure-dependent phase transition behavior of water in different types of food materials (Tylose, potato, salmon fish, pork, and pure water). Small samples (0.48–0.72 g, vacuum-packaged in polyethylene pouches) of these materials were tested through isothermal pressure scan ( P-scan, 0.3 MPa min −1) at various sub-zero temperatures. P-scan tests produced reliable information on phase transition and latent heat in test foods at elevated pressure. Polynomial regression equations were established to express numerical relationship between pressure and phase change temperature or latent heat for these test materials. It was indicated that phase transition point (either temperature or pressure) in foodstuffs was significantly depressed ( P < 0.05) as compared with that in pure water. Latent heat measured during P-scan of food materials had a trend different from that of pure water due to the temperature dependence of ice content in frozen foods. Ice-mass based latent heat showed insignificant difference ( P > 0.05) from the latent heat between pure water and ice I under pressure. Moisture content was a major factor affecting phase transition and latent heat during pressure processing of foods. As a higher moisture material, potato demonstrated a higher phase transition point and a higher latent heat during a P-scan test at fixed temperature. P-scan technique is a powerful technique to successfully understand pressure-dependent phase transition phenomena in food products during HP processing.