Impact of sanitizer application on Salmonella mitigation and microbiome shift on diced tomatoes during washing and storage

Salmonella enterica is a major foodborne pathogen associated with consumption of fresh tomatoes, and Salmonella contamination during post-harvest handling has been suspected and implicated in multiple food-borne illness outbreaks. This study examined the shift in Salmonella and indigenous microbiota on diced tomatoes after washing with different sanitizers and during storage. Roma tomatoes were inoculated with a Salmonella cocktail at 8 log CFU/mL, diced and washed along with non-inoculated diced tomatoes in simulated flume wash water with sanitizers, including 10 mg/L free chlorine (C10), 90 mg/L peracetic acid (P90), P90 plus a sulfuric acid surfactant (PP), and un-sanitized control (K). Salmonella, total bacteria, and yeast and mold (YM) populations on both inoculated and non-inoculated samples were measured before, after washing and during storage at 4 C. 16S rRNA high-throughput sequencing was also performed to determine shift in bacterial microbiome. Washing with all tested sanitizers, especially PP, efficiently reduced Salmonella and bacterial populations on inoculated diced tomatoes after washing. Application of sanitizers significantly mitigated Salmonella cross-contamination on non-inoculated samples. PP treatment inhibited the proliferation of most dominant bacteria on diced tomatoes during storage, such as Erwiniaceae, Curtobacterium, Pantoea, Erwinia and Enterobacterales, which may benefit product quality and safety. YM populations were generally similar among washing treatments with sanitizers. This study provides in-depth information about the microbial ecology of the diverse bacterial communities on diced tomatoes during washing and the subsequent storage, which can help guide further studies on the interactions of microbes on produce, the prevention of contamination with Salmonella, plant pathogens and spoilage bacteria.