Reduction of Pathogen Surrogate Bacteria using BioSafe® , an Aqueous Ozone Intervention, on Diced Fruits and Vegetables

Karla M. Rodriguez, David A. Vargas, Marcos X. Sánchez-Plata, Mindy M. Brashears, Dan Lynn, and Markus F. Miller

Introduction: Due to recent Shiga-Toxin Producing E. coli (STEC) and Salmonella outbreaks associated with produce, the produce industry is continuously evaluating a combination of preventive systems and intervention strategies to mitigate the risks of pathogens that can cause foodborne illness.

Purpose: To determine the antimicrobial efficacy of BioSafe aqueous ozone intervention applied to frozen and fresh fruits and vegetables challenged with pathogenic E. coli surrogates.

Methods: A cocktail of five non-pathogenic strains of E. coli (ATCC BAA 1427, 1428, 1429, 1430, and 1431) that were reported as suitable surrogates for Salmonella and E. coli O157:H7 was used to inoculate the surface of fruits and vegetables (Blueberries, Carrots, Lettuce, Spinach and Broccoli) at ~ 5-LogCFU/g. BioSafe® ozonated water treatment was applied at an oxidation reduction potential (ORP) > 850mV. For each fruit and vegetable twenty, 25 g samples were treated using a plastic spray bottle with the E. coli surrogate cocktail and 20 minutes were allowed for cell attachment. From each product, 10 uninoculated samples were tested for aerobic counts (AC) to enumerate natural microbiota and 20 inoculated samples were collected before and after BioSafe treatment spray and enumerated using the Tempo® System for Aerobic Counts (AC) and E. coli Count (EC) methods. A t-test was performed using R software (Version 4.04).

Results: Natural microbiota was between 2.12, and 5.58(LogCFU/g). E. coli counts (LogCFU/g) were significantly reduced (P < 0.001) between attachment and after BioSafe treatment on average by 1.32, 2.08, and 1.58 LogCFU/g on blueberries, lettuce, and spinach, respectively. E. coli counts (LogCFU/g) on broccoli and carrots were not significantly reduced comparing attachment and after-treatment samples.

Significance: Aqueous ozone intervention treatment was shown effective in our challenge trial for blueberries, lettuce and spinach indicating it can be applied in industrial scale as an intervention to reduce potential contamination with pathogens. Based on the data, it is reasonable to conclude that the spray treatment is effective in reducing Salmonella spp. and E. coli in blueberries, lettuce and spinach. Use of ozone must be optimized for each treatment and additional optimization is needed for other produce before use.

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