Efficacy of Chlorine Dioxide Gas to Decontaminate Fresh Produce Used for In-store and Vendor Juicing Operations

Introduction: Unpasteurized juices are increasingly popular as consumers aim to find convenient, healthy menu options. Contamination of produce with pathogens such as Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes poses a risk. In-store treatment of small batches of mixed types of fresh produce with chlorine dioxide gas may prove effective in decontaminating produce before preparing juices. 

Purpose: The purpose of this study was to determine the effectiveness of chlorine dioxide gas generated in self-contained sachets suitable for use in retail operations to reduce levels of Salmonella, E. coli O157:H7, and L. monocytogenesin mixed produce containers. 

Methods: A mixed cocktail of five strains of Salmonella, E. coli O157:H7, and L. monocytogenes was spot inoculated on injured and uninjured oranges, kale, celery, and cucumbers. Produce was treated together in batches with 20 mg/kg ClO₂gas, 200 ppm chlorine, or 80 ppm peracetic acid; non-gas and water controls were also included. Two samples of each produce type from each treatment were subjected to microbiological analysis. Reductions of pathogens were compared through a random effects model with interactions.

Results: There were significant differences (p<0.05) between type of produce, microorganism, injury status, and treatment though treatment type proved to be the major source of variance. ClO₂ gas treatment on average for all produce types, microorganisms, and injury status produced a log reduction of 2.66 which was significantly different from all other treatments and controls. Peracetic acid and chlorine treatments were not found to be statistically different and produced 1.96 and 1.89 log reductions, respectively. The largest log reduction of 3.70 was with E. coliO157:H7 on injured kale that received gas treatment. 

Significance: ClO₂ gas generated in self-contained sachets may be a practical, convenient delivery method and superior to commonly used sanitizers in decontaminating mixed types of produce used in retail juicing operations.