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C. M. CORVALAN1, G. Chen2, and O. H. Campanella2. (1) Dept. of Food Science, Purdue Univ., 745 Agriculture Mall Dr., West Lafayette, IN 47907-2009, (2) Dept. of Agricultural & Biological Engineering, Purdue Univ., 1146 Agricultural & Biological Engineering Bldg., West Lafayette, IN 47907-1146 IFT's second Research Summit resolution suggests that the assumption of linear semi-logarithmic microbial survivor curves may not satisfy modern food industry requirements. Recent analysis of inactivation data from a wide range of microorganisms have confirmed that most semi-logarithmic survivor curves tend to present an upward or downward concavity that follows a weak power law dependence. This power law dependence indicates that linear semi-logarithmic curves would not be well suited for the design of optimal inactivation processes. The objective of this study was to develop a predictive model of microbial inactivation able to describe the power law dependence exhibited by many microorganisms when exposed to lethal agents. This model would allow better prediction of microbial inactivation for design of optimal food processes In this study we developed a new kinetic model for microbial inactivation using methods of fractional calculus. Fractional calculus is a modern branch of mathematics that provides a natural framework for describing power law relationships that are frequently present in biological processes. Our results showed that predictions from the fractional kinetic model provide a close fit of experimental isothermal inactivation data and is well suited for design of non-isothermal inactivation processes. The results of this study suggest that fractional kinetic may provide a new view of kinetic processes and a useful generalization to the classical linear first-order kinetic model able to describe the observed power law deviation and predict microbial inactivation more realistically. More important, fractional inactivation offers a natural unifying approach linking first order kinetics and power law inactivation models. A secondary but important advantage of the fractional kinetic model is that can be described by a integral relationship which is numerically better suited for the design of non-isothermal inactivation processes than current differential models.
Session 111, Food Engineering: Modeling heat transfer and microbial inactivation
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