Quasi-adiabatic temperature increase during high pressure processing of selected foods

The effect of food composition on the quasi-adiabatic temperature increase during high pressure processing (HPP) was studied using specially designed experimental equipment. delta(s) was evaluated as the ratio of the temperature increase with respect to final pressure. Selected foods (mayonnaise dressing, egg yolk raw fresh, egg white raw fresh, Hass avocado, beef ground 90% lean meat, chicken breast fat free raw. whole and skim milk, gravy beef canned) were evaluated at an initial temperature of 25 degrees C and pressure treatments ranging from 150 to 600 MPa. The effect of initial temperature (1-70 degrees C) on the delta(s) over a range of pressures treatments from 150 to 600 MPa was evaluated using vegetable oil, honey and cream cheese. Results showed that vegetable oil had the highest delta(s) (upto 9.7 degrees C/100 MPa) of the samples examined. This delta(s) value decreased with increasing pressure and was slightly affected by initial temperature of the sample. For foods with high water content, delta(s) increased with increasing initial temperature. An empirical equation was developed to calculate the final temperature during HPP at different initial temperatures for vegetable oil, honey and cream cheese. The observed thermal effects of compression must be taken into account when HPP sterilization or pasteurization processes are developed. (c) 2006 Elsevier Ltd. All rights reserved.