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D. F. FARKAS, Department of Food Science and Technology, Oregon State University, 100 Wiegand Hall, Corvallis, OR 97311-6602, D. G. HOOVER, Department of Animal and Food Sciences, University of Delaware, 035 Townsend Hall, Newark, DE 19717-1303, and J. L. Kokini, Food Science Department, Rutgers University, P.O. Box 321, New Brunswick, NJ 08903-0231.

High pressure processing (HPP) subjects foods to pressures between 100 and 800 MPa (megaPascals) (15,000 to 120,000 psi) to inactivate vegetative bacteria, yeasts, molds and parasites. Factors that affect the rate of microbial inactivation, approximately in order of importance, are; pressure magnitude, microbial type and growth stage, temperature, pH, water activity, and food composition. Examples of microbial inactivation using HPP technology will be described for jams, orange juice, and meat products. HPP in combination with heat and antimicrobial additives has also proved successful in the inactivation of vegetative microorganisms and to some extent bacterial spores. Microbial inactivation mechanisms and mathematical models for inactivation kinetics, based on these mechanisms, will be discussed. Validation of HPP processes, including measurement of critical factors, HACCP, and use of microbial surrogates, also will be addressed. This presentation will also include a discussion of the potential of ultrasound for food preservation. Ultrasonic applications appear best suited to evaluate the internal quality and composition of foods rather than for microbial inactivation. Sonication may have more potential applications in the future if combined with other preservative processes.