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Challenges, opportunities and synergies in applications of high pressure to food processing |
C. P. DUNNE, U.S. Army Natick Soldier Center, U.S. Army Research, Development & Engineering Command, Combat Feeding Innovative Science Team, Kansas St., Bldg. 36, Rm. E-108, Natick, MA 01760-5020 The U.S. Army Natick Soldier Center has been involved with the development and evaluation of nonthermal processes employing high hydrostatic pressure (HHP). A strategic approach and a set of criteria guide the development of potential shelf-stable prototype foods produced by this novel processing technology. Meeting key criteria involving: 1) Microbiological Safety & Stability, and 2) Chemical/Physical/Biochemical Stability requires knowledge of the environmental determinants of the interactions of pressure with both microorganisms and their matrices. Experiments based upon the hypothesis that a primary target for inactivation of vegetative microorganisms by HPP is the functional bacterial cell membrane have demonstrated that both temperature and pH have a major impact on microbial inactivation kinetics. The operational goal for HHP pasteurization to achieve a reduction of 5 to 6 logs of vegetative bacterial populations most likely to be found in the chosen food material has been met in a variety of foods. A reduction in the treatment time or pressure required to achieve equivalent levels of bacterial kill or injury may be accomplished by HPP at modestly elevated temperatures or at pH of < 5. HPP can produce shelf-stable foods with pH of <=4.2 and extended shelf life refrigerated foods. Optimization of HPP treatment for commercial sterilization by inactivation of bacterial spores demands knowledge of pressure-induced adiabatic heating and potential interactive and possibly synergistic effects on ionic and other equilibria in food or experimental media as well as upon the target organisms. Additional synergistic effects for HPP exploit use of a number of membrane-active compounds including bacteriocins or surfactants. Better knowledge of the impact of pressure upon spore structure along with plausible kinetic models and mechanistic hypotheses are required before commercial sterilization of low-acid foods is attained. HPP offers potential for pressure to have impact on structure and function of key spore proteins.
Session 7, Science-based applications of high pressure processing in the food industry
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