Use of high-concentration-short-time chlorine dioxide gas treatments for the inactivation of Salmonella enterica spp. inoculated onto Roma tomatoes

Salmonella outbreaks have been recently linked to the consumption of fresh tomatoes. Thus, there is a need to develop systems that reduce the risk of microbial contamination to increase product shelf-life and keep fresh fruit attributes. The objectives of this study were to evaluate high-concentration-short-time chlorine dioxide gas treatments effects on Salmonella-inoculated Roma tomatoes and determine the optimal treatment conditions for microbial inactivation and shelf-life extension. Effects of ClO2 concentration (2, 5, 8 and 10 mg/l) and exposure time (10, 30, 60, 120 and 180 s) on inoculated Roma tomatoes were studied. Salmonella enterica strains, serotype Montevideo, Javiana and Baildon, were used to experimentally inoculate the food product. After ClO2 treatments, tomatoes were stored at room temperature for 28 days. Inherent microbial population, change in tomato color, and chlorine dioxide gas residuals were evaluated. ANOVA analysis showed that both ClO2 concentration and treatment time were significant (p < 0.01) for Salmonella inactivation. Surviving Salmonella populations of 3.09, 2.17 and 1.16 log CFU/cm2 were obtained treating tomatoes with 8 mg/l ClO2 for 60 s, 10 mg/l ClO2 for 120 s, and 10 mg/l for 180 s, respectively (initial Salmonella population: 6.03 ± 0.11 log CFU/cm2). The selected treatments significantly reduced background microflora (p < 0.05), while fruit color and residual contents were not significantly different (p > 0.05), as compared to the control. Results suggest the potential for high-concentration-short-time treatments ClO2 gas as an effective pathogen inactivation technology for large-scale produce packing operations.