28-3 |
Compression heating of selected food substances during high pressure processing |
V. Rasanayagam1, V. M. BALASUBRAMANIAM1, E. Y. Ting2, C. E. Sizer1, C. Bush2, and C. Anderson2. (1) National Center for Food Safety & Technology, Illinois Institute of Technology, 6502 S. Archer Rd., Summit-Argo, IL 60501, (2) Flow International Corp., 23500 64th Ave. S., Kent, WA 98032 High pressure processing (HPP) provides the potential for processing low-acid foods at combination of elevated pressures and temperatures which promote minimal thermal degradation. Very limited information is available on compression heating characteristics of various food materials under HPP conditions. To characterize compression heating properties of food materials during HPP. Compression heating of different food material during HPP was studied using a specially fabricated experimental setup. The setup utilized a 25-HP high-pressure pump,which enabled instantaneous pressure come-up and depressurization times. Compression heating behavior various food materials including soy bean oil, olive oil, glycol/water mixture, beef fat, chicken fat, mashed potato, orange juice, tomato salsa, fresh salmon flesh and water with up to 600 MPa were studied. Initial product temperature was kept at 25oC for all the trials. Temperature raise due to adiabatic compression heating depends primarily up on the target pressure, product compressibility, and initial temperature. But the apparent product temperature rise in a process vessel is also influenced by rate of heat loss to pressure media and the surroundings. Among the materials tested, water gave the lowest temperature rise (2.8 - 3oC per 100 MPa) at all pressure levels and olive oil (8.7 to 6.3oC per 100 MPa) and soybean oil (9.1 to 6.2oC per 100 MPa) gave the highest temperature rise. The temperature increase in water was very close (1.13oC) to the values predicted by NIST standard reference database (Version 2.2, NIST, Boulder, CO). Oils exhibited nonlinear behavior with temperature change at higher pressures. Within the range of conditions studied, water is likely to have the lowest compression heating. Change in product or pressurization media temperature as a result of compression heating and subsequent heat transfer should be considered during HPP microbial inactivation studies in media of different composition, especially those involving bacterial spores.
Session 28, Nonthermal Processing: Food safety and quality aspects of nonthermal processing technologies
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