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<OL> <LI> Obtain viable count data from microorganisms in foods during pressure treatment using appropriate plating media at different treatment pressures and different initial temperatures over a time period long enough to examine any tailings (resistant subpopulations). <LI> After determining the rate, frequency and conditions for generation of resistant organisms, evaluate the effect of low initial treatment temperature.<LI> Determine the extent that culture age affects inactivation kinetics involving pressure treatment conditions. <LI> Analyze data compiled from this study: Determine D values assuming first-order kinetics, also predict and fit using nonlinear models for selection of best predictive model.
This research project will provide information germane to appropriate processing parameters which can be applied to assure the microbiological safety of foods preserved using HPP. Modeling the information will provide a summary of the experimental data for use in future commercial applications. This will increase in importance as HPP becomes more readily accepted by the food industry. U.S. and international consumers are demanding minimally processed foods that resemble raw or fresh-like products in sensory quality (e.g., flavor, texture and appearance) and nutrient content as compared to their highly heat-processed counterparts, while retaining similar levels of safety and convenience. This project will specifically address the nonlinear nature of HPP-derived semilogarithmic survival curves. Since a logarithmic (first-order) rate of death is normally assumed in the predictive microbiology of HPP, there is a food safety concern associated with extrapolation of the process end-point beyond the linear region. This practice carries the danger of underestimating HPP-resistant organisms remaining in the processed food. Since limited experience and history exist on use of HPP in the production of large quantities of food, the reliance on first-order kinetics to project the level of risk and process effectiveness warrants examination to ensure the safety of HPP foods.