Chlorine dioxide gas and ozone: Novel surface sanitizers for green peppers
Abstract
There are increasing concerns about fruits and vegetables because of outbreaks caused by pathogens, including Escherichia coli O157: H7 and Listeria monocytogenes Scott A. However, traditional sanitation methods (washing with chlorinated water) are not effective to decontaminate fruits and vegetables. Highly effective sanitizers, such as gaseous chlorine dioxide (ClO2) and ozone are two effective alternatives to chlorine. ClO2 and ozone gases effectively inactivated E. coli O157: H7 and L. monocytogenes on green peppers. A 7.3 log reduction of E. coli O157: H7 and a 6.3 log reduction of L. monocytogenes on uninjured pepper surfaces were achieved after a 0.6mg/l ClO2 gas treatment for 30 min at 22°C and 95% relative humidity (RH). ClO2 gas treatment was much more effective than aqueous ClO2 treatment and water washing. More than 6 log L. monocytogenes on uninjured surfaces and about 3.5 log on injured surfaces were inactivated by a 3 mg/l ClO2 gas treatments for 10 min at 20°C. A 3 mg/l aqueous ClO2 treatment achieved 3.7 and 0.4 log reductions on uninjured and injured surfaces, respectively; whereas, water washing alone reduced 1.4 and 0.4 log L. monocytogenes, respectively. The significant difference (P < 0.05) between log reductions of E. coli O157: H7 and L. monocytogenes on uninjured surfaces compared to injured surfaces suggested that injured surfaces protected bacteria from ClO2 gas treatments. Results from colony enumeration, scanning electronic microscopy and confocal laser scanning microscopy studies suggested that bacteria preferentially attached to injured surfaces, and that the injuries to pepper surfaces increased bacterial adhesion, growth, and resistance to water washing and ClO2 gas treatment. A membrane transferring plating method was the preferred method for resuscitation and enumeration of ClO2-injured E. coli O157: H7 and L. monocytogenes. Using response surface methodology, the inactivation of E. coli O157: H7 on green peppers by ClO2 and ozone was modeled. Statistical analysis showed that ClO 2 gas or ozone concentration (the most important factor), RH, and time all significantly (P < 0.01) increased the inactivation of E. coli O157: H7. A statistically synergistic interaction between ClO 2 gas or ozone concentration and RH was significant (P < 0.1 or P < 0.05).
Degree
Ph.D.
Advisors
Nielsen, Purdue University.
Subject Area
Food science
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