The effectiveness of closed-circulation gaseous chlorine dioxide or ozone treatment against bacterial pathogens on produce food control

Authors: Bridges, David; RANE, BHARGAVI - University Of Maine; Wu, Vivian

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/4/2018
Publication Date: 4/13/2018
Citation: Bridges, D.F., Rane, B., Wu, V.C. 2018. The effectiveness of closed-circulation gaseous chlorine dioxide or ozone treatment against bacterial pathogens on produce food control. Food Control. 91(2018):261-267. https://doi.org/10.1016/j.foodcont.2018.04.004.
DOI: https://doi.org/10.1016/j.foodcont.2018.04.004

Interpretive Summary: Contamination of fresh produce can occur anywhere from farm to fork. In the pre-harvest environment, microbial contaminates can come from numerous sources including irrigation water, soil, fertilizers, and even insects. After harvest, pathogen contamination of fresh produce can occur through improper handling, improperly cleaned surfaces and equipment, or from lack of appropriate hygiene practices in processing or preparation environments. Chlorine, in concentrations ranging from 50-200 ppm, is the most commonly added antimicrobial to these washes. However, chlorine solutions have been reported to be ineffective. Furthermore, the occupational health hazard associated with chlorine use, negative environmental impacts, and a reported inability to reduce pathogens internalized in plant tissues has led to a trend to use safer and more effective antimicrobials to treat produce. Gaseous treatments use little, if any, water and are capable of treating areas and irregularities on produce surfaces that aqueous antimicrobials have difficulty reaching. This study compared the effectiveness of gaseous chlorine dioxide and ozone treatment against Shiga toxin-producing Escherichia coli (STEC), Salmonella enterica serovars, and Listeria monocytogenes on baby-cut carrots, lowbush blueberries, and beefsteak tomatoes using closed-circulation treatment system. These results indicated that gaseous chlorine dioxide was more effective than ozone and can be a suitable treatment when implemented correctly to reduce bacterial pathogens in a storage setting.

Technical Abstract: The objective of this study was to compare the effectiveness of gaseous chlorine dioxide (ClO2) and ozone (O3) treatment against Shiga toxin-producing Escherichia coli (STEC), Salmonella enterica serovars, and Listeria monocytogenes on baby-cut carrots, lowbush blueberries, and beefsteak tomatoes using closed-circulation treatment system. Dry ClO2 precursor were combined in-chamber to make 0.03, 0.06, and 0.12 mg ClO2/g produce for a 2.5 h exposure and 0.04, 0.07, and 0.15 mg ClO2/g produce for a 5.0 h exposure time. Ozone was generated through corona-discharge of a dry oxygen feed and either 0.4 or 0.8 mg O3/g produce concentrations were used to treat the produce-mass for 2.5 and 5.0 h. Overall, ClO2 treatment was the more effective treatment with maximum bacterial reductions of > 7 log CFU/g observed on carrots and tomatoes and 3.7 CFU/g on blueberries. Comparatively, maximum reductions of 1.2, 1.8, and 1.6 log CFU/g were only achieved after 5 h exposure to 0.8 mg O3/g produce. This treatment simultaneously resulted in noticeable bleaching carrot and tomato tissue as well. These results reported here indicate that gaseous ClO2 can be a suitable treatment when implemented correctly to reduce bacterial pathogens in a storage setting.