Efficacy of ozone produce washers in reducing natural and artificially inoculated microorganisms on roma tomatoes and green onions

This study investigated the efficacy of ozone washing appliances for microbial decontamination of tomatoes and green onions. Produce were submerged for light or heavy washing in ozone Washer-A or -B (Washer-B generates higher levels of ozone and agitation) or non-ozone Washer-C. Ozone washings reduced total aerobic mesophile counts on whole tomatoes but not green onions when compared to unwashed samples. Washer-B at heavy setting reduced coliform numbers on whole tomatoes by 1.9 cfu/g. Furthermore, Washer-B yielded more than 2.0 log reductions of Escherichia coli (inoculation level at ∼6.3 log cfu/g) on the edible portions of tomatoes than Washer-A at comparable settings. A follow-up study using Washer-B showed that ozone application can significantly reduce E. coli and Salmonella in produce wash water to prevent cross-contamination. However, when compared to non-ozone washing of produce, improved reduction of natural and artificially inoculated microorganisms by ozone applications was not found. Microscopic observation corroborates microbial enumeration showing that removing inedible portions (stem scars or root bulbs) of washed tomatoes and green onions is beneficial for microbial decontamination.

Contaminated produce is a major cause of bacterial-related foodborne illnesses in the U.S.A.  To meet consumer’s demand for safer produce, effective sanitizing methods need to be developed and verified. Data from this study expands our knowledge of ozone-based kitchen appliances for produce sanitization and their practical value for preventing cross-contamination during produce washing. Furthermore, the findings highlight the importance of removing stem-scar and root bulb portions of washed produce for food safety.

This paper can be purchased from the Journal of Food Science. Click here for link.