88E-7 |
Response surface modeling for the inactivation of Escherichia coli O157: H7 on green peppers ( Capsicum annuum ) by gaseous chlorine dioxide and ozone treatments |
Y. HAN1, J. D. Floros, R. H. Linton, S. S. Nielsen, and P. E. Nelson. (1) Food science, Purdue University, 1160 Food Science Building, West Lafayette, IN 47907 Abstract There are increasing concerns about minimally processed and refrigerated (MPR) fruits and vegetables because of outbreaks caused by pathogens, including Escherichia coli O157:H7. Nonthermal treatments, such as gaseous chlorine dioxide (ClO2) and ozone, could be effective as alternative methods for reducing pathogens. Our objectives were to: (a) determine the effect of ozone and ClO2 gas concentration, relative humidity (RH), time, and temperature on the inactivation of E. coli O157: H7 on green peppers, and (b) develop predictive models using response surface methodology. Green peppers were inoculated with 7-8 log cfu/5g cells, then treated with 0.1-0.5 mg/l ClO2 gas for 7-135 min at 5-25oC and under 55-95% RH, or treated with 2-8 mg/l ozone for 10-40 min at 25oC under 60-90% RH. A four-factor central composite rotatable design and a three-factor Box-Behnken plan were used for ClO2 gas and ozone treatments, respectively. Microbial log reduction was measured as a response. A membrane-transferring-plating method with tryptic soy agar and sorbital MacConkey agar was used for resuscitation and enumeration of bacteria treated with ClO2 and ozone. Statistical analysis suggested that ClO2 and ozone concentration, time, RH, and temperature all significantly (P<0.01) increased the rate of microbial destruction. For ClO2 treatments, concentration was the most important factor, while temperature was the least significant. For ozone treatments, concentration also provided the greatest effect on bacterial inactivation, while RH had the least important effect. Both ClO2 gas and ozone concentration exhibited a synergistic interaction with RH. Both predictive models were validated and could be used to determine effective ClO2 gas and ozone treatments to achieve 5 log reductions of E. coli O157: H7 on green peppers. ClO2 gas and ozone are promising techniques for microbial reduction in MPR foods.
Session 88E, Fruit & Vegetable Products: Processing
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