Purpose: Consequently, this study aimed to assess the redistribution of Salmonella Typhimurium LT2 during pilot-scale production of fresh-cut baby spinach and cilantro.
Methods: 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/leaf) were used with spot-inoculated red leaf lettuce serving as a colored surrogate for baby spinach and cilantro. For each of three trials per condition, 5 kg batches of product containing uninoculated baby spinach or cilantro and inoculated red leaf lettuce at each of the aforementioned ratios and inoculation levels was washed for 90 sec in a 3.3-m long flume tank through which 890 L of sanitizer-free tap water was circulated in a pilot-scale leafy green processing line. After washing and removing the red leaf lettuce, all previously uninoculated product (~23 samples/250 g each) was analyzed for presence/absence of Salmonella using the Salmonella GeneQuence Assay (Neogen Corp. Lansing, MI).
Results: Overall, 100% of the spinach samples washed with red leaf lettuce containing Salmonella at 10³ CFU/g tested positive, regardless of the inoculated:uninoculated ratio. When red leaf lettuce was inoculated at 10¹ CFU/g, 100, 64-81, 52-61 and 12-22% of the samples yielded Salmonella at inoculated:uninoculated ratios of 10:100, 5:100, 1:100, and 0.5:100, respectively. At the lowest inoculation level of 10⁻¹ CFU/g, 4.3-8.7, 4.3-8.7, 4.3-26.0 and 0% of the samples yielded Salmonella at inoculated:uninoculated ratios of 10:100, 5:100, 1:100, and 0.5:100, respectively, with a similar trend seen for cilantro.
Significance: This is the first study to assess the spread of Salmonella from incoming product to baby spinach and cilantro during processing. These results provide important data for microbial risk assessments associated with leafy greens.