44G-26 |
The roles of oxidation-reduction potential (ORP) and residual chlorine in killing foodborne pathogens |
C. KIM and Y. C. Hung. Dept. of Food Science & Technology, Univ. of Georgia, Center for Food Safety & Quality Enhancement, 1109 Experiment St., Griffin, GA 30223 Electrolyzed (EO) water has been reported having strong microbicidal effect. This study was undertaken to evaluate the roles of oxidation-reduction potential (ORP) and residual chlorine in EO water and chlorinated water for the inactivation of Listeria monocytogenes. L. monocytogenes Scott A (109 CFU/ml) was subjected to deionized water (control), EO water (30 ppm chlorine), and chlorinated water (30 ppm chlorine) treatments. Neutralizing buffer solution was added to EO and chlorinated water to neutralize chlorine while still maintaining high ORP. Complete inactivation of Listeria occurred within 60 sec after EO and chlorinated water treatments. Addition of 0.1 ml neutralizing buffer solution to 100 ml EO water completely neutralized chlorine while still maintaining high ORP (1,003 mV) and this solution achieved 6 log reduction on Listeria. For 100 ml of chlorinated water, 8 ml neutralizing buffer solution was needed to reduce chlorine to trace level and ORP of 853 mV. Listeria was detected only by enrichment after this modified chlorined water treatment. The modified chlorinated water was more effective than the modified EO water and may be due to the trace amount of chlorine remaining in the modified chlorine solution. To further investigate the role of ORP for inactivation of L. monocytogenes, Listeria was treated with EO water with different ORP levels (1,000 to 900 mV) but with no residual chlorine. EO water with ORP of 1,000 mV reduced Listeria population by 6 log, whereas EO water with ORP of 900 mV was ineffective. This study suggests that both ORP and chlorine are important for microbial inactivation. ORP level in the solution needs to be maintained at above 1,000 mV if no chlorine is present. ORP level in the solution can be reduced to 850 mV with trace amount of chlorine while still maintaining the microbicidal effect.
Session 44G, Toxicology & Safety Evaluation
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