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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 ASABE. Vol. 47(1): 173-181 . @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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