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MODELING THE INACTIVATION OF ESCHERICHIA COLI O157:H7 ON INOCULATED ALFALFA SEEDS DURING EXPOSURE TO OZONATED OR ELECTROLYZED OXIDIZING WATER

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org

Citation:  Transactions of the ASAE. 47(1): 173-181. (doi: 10.13031/2013.15845) @2004
Authors:   R. R. Sharma, A. Demirci, V. M. Puri, L. R. Beuchat, W. F. Fett
Keywords:   Alfalfa, E. coli O157:H7, Inactivation, Modeling, Ozone, EO water

Alfalfa sprouts contaminated with Escherichia coli O157:H7 and Salmonella have been implicated in a number of foodborne disease outbreaks in recent years. Seeds are attributed to be the main source of contamination for sprouts. Data from studies on the treatment of E. coli O157:H7 inoculated alfalfa seeds with ozonated and electrolyzed oxidizing (EO) water were used to develop models for predicting inactivation of the pathogen. Treatment times of 0 to 16 min were used for ozonated water at initial concentrations of 0 to 21 ppm. For EO water treatments, 0 to 19 amperage (A) data at treatment times of 0 to 32 min were used to develop the models. A modified Monod model for bacterial death kinetics was developed by integrating the rate constant (k) as a Lorentzian function of treatment time (t). Regression constants for the Lorentzian function were determined at various ozone concentrations (ppm) or A. Validation showed that the model was an effective predictor at ozone concentrations below 8 ppm. As a second method, a response surface model (RSM) was utilized for which an RSM regression was performed between observed log10N/No and ppm (ozone) or A (EO water) and treatment time. A quadratic equation involving linear, quadratic, and interaction terms of the influencing parameters represented the model for ozonated and EO water treatments. The models were validated by back predicting log10N/No values. Although numerous other factors influence the accuracy of prediction of the models, these models can be useful tools to researchers and regulators for the development of improved seed sanitizing guidelines by facilitating assessment of efficacy of a treatment and enhancing food safety.

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