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

Author
item SHARMA, RATNA - PENN STATE UNIVERSITY
item DEMIRCI, ALI - PENN STATE UNIVERSITY
item PURI, VIRENDRA - PENN STATE UNIVERSITY
item BEUCHAT, LARRY - UNIVERSITY OF GEORGIA
item Fett, William

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2003
Publication Date: 1/1/2004
Citation: SHARMA, R.R., DEMIRCI, A., PURI, V.M., BEUCHAT, L.R., FETT, W.F. MODELING THE INACTIVATION OF ESCHERICHIA COLI O157:H7 ON INOCULATED ALFALFA SEEDS DURING EXPOSURE TO OZONATED OR ELECTROLYZED OXIDIZING WATER. TRANSACTIONS OF THE AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS. 2004. V. 47(1). P. 173-181.

Interpretive Summary: Alfalfa sprouts contaminated with Escherichia coli O157:H7 have been implicated in several outbreaks during recent years. Improved methods of decontaminating sprouting seed are required. In this study we used the results of previous experiments that examined the efficacy of two types of antibacterial solutions for seed decontamination. The first solution was prepared by addition of the antibacterial compound ozone to water. The second solution was obtained by passing an electric current through salt water to give what is called electrolyzed oxidizing water. The data was used to develop two types of models for predicting inactivation of the pathogen. Both types of models accurately predicted the efficacy of such antibacterial seed treatments. This information will be useful in the development of more effective seed decontamination protocols required to help ensure the microbial safety of alfalfa and other type of sprouts for the consuming public.

Technical Abstract: 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 amp 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 Lorentzian function were determined at various ozone concentrations (ppm) or amperage (amp). Validation showed that the model predicted well 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 amp (EO water) and treatment time. A quadratic equation involving linear, quadratic, and interaction terms of the influencing parameters represented the model for ozone and EO water treatments. The models were validated by back predicting log10N/No values. 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.