Efficacy and Reproducibility of a Produce Wash in Killing Salmonella on the Surface of Tomatoes Assessed with a Proposed Standard Method for Produce Sanitizers

Abstract

The reproducibility of a method developed to evaluate point-of-use sanitizers for fresh produce was tested at three different laboratories. Mixtures of five Salmonella serotypes were inoculated on the surface of ripe tomatoes. After the inoculum was dry, tomatoes were placed inside a plastic bag and sprayed with sterile USP water, Dey and Engley (D/E) neutralizer broth, or a prototype Fit produce wash (PW), an alkaline solution comprised of generally recognized as safe ingredients (water, oleic acid, glycerol, ethanol, potassium hydroxide, sodium bicarbonate, citric acid, and distilled grapefruit oil), and rubbed for 30 s. The tomatoes were rinsed 10 s with 195 ml of D/E neutralizer broth (rinse solution), then combined with 20 ml of D/E neutralizer (residual wash solution) and rubbed by hand to remove residual Salmonella. Populations of Salmonella were determined for each tomato in the rinse solution and residual wash solution. Treatment with PW resulted in reductions in the number of Salmonella 2 to 4 logs greater than those achieved with the sterile water or D/E neutralizer broth controls. Consistent results were obtained across the three study sites, indicating reproducible results were obtained using the test method. The method used to determine the efficacy of killing or removing Salmonella from tomatoes in this study is suggested as a standard method for measuring the efficacy of sanitizers on tomatoes and other similar fruits and vegetables with rigid, smooth surfaces.