Salmonella typhimurium LT2 transfer and redistribution on baby spinach and cilantro during pilot-scale processing

Several recent outbreaks traced to baby spinach and cilantro have been hypothesized to involve cross-contamination during washing and processing. Consequently, this study aimed to assess the redistribution of Salmonella Typhimurium LT2 during pilot-scale production of fresh-cut baby spinach and cilantro. Four inoculated:uninoculated product weight ratios (0.5:100, 1:100, 5:100, and 10:100) and three different inoculation levels (103, 101, and 10-1 CFU/g) were used with spot-inoculated red leaf lettuce serving as a colored surrogate for baby spinach and cilantro washing. Sanitizer-free wash water was used for all trials and a chlorine-based sanitizer was used at 60 ppm available chlorine only for the highest inoculation level (103 CFU/g) and the three highest weight ratios (1:100, 5:100, and 10:100). Overall, initial inoculation level had a greater impact on the amount of Salmonella-positive samples than the weight ratios examined for both commodities. The number of positive samples concurrently decreased as the initial inoculation level of the surrogate decreased. Within each inoculation level, no significant differences (P > 0.05) were found among the four product ratios. This is the first study to assess the spread of Salmonella from incoming product to baby spinach and cilantro during processing. These results will provide important data for microbial risk assessments associated with leafy greens.