Background and Aim: Every year, foodborne disease costs the United States millions of dollars in health care and food recalls. Millions of Americans acquire foodborne illness, which may result in lost work and productivity, hospitalization, and death. Food safety research is ongoing, and all data helps decrease the risk of the spread of foodborne disease. However, there remain gaps in the literature knowledge. Specifically, the percent transfer rates of curly kale and intact grape tomato have not, yet, been studied. Similarly, the fate of human pathogens on these two produce variants has not been assessed and quantified. Finally, though some data has been collected on the percent retention rate of bamboo cutting boards, the data has been inconsistent and broad. In addition, pressed paper cutting surfaces have not been assessed for retention, and the extent to which cutting surface damage may impact retention rate has not been considered in any of the current literature. Therefore, the purpose of this study is to assess the transfer rates of curly kale and grape tomato, along with the retention rates of both intact and damaged bamboo and pressed paper cutting surfaces. Additionally, this study quantifies the persistence of human pathogens on kale and tomato at two storage temperatures.
Methods: Selected strains of Listeria monocytogenes and Salmonella enterica spp. were mixed in cocktail and were used to inoculate cutting surfaces before produce was pressed with consistent, mechanical pressure for a finite duration, to simulate common kitchen practices of stabilizing produce against cutting boards. Both surfaces and produce were processed in BPW by massage and sonication. Solutions were serial diluted and plated on selective agar. Plates were incubated at 37°C for 24 hours and then enumerated to assess percent transfer and percent retention. Data were analyzed in R Studio, using non-parametric tests to consider statistical significance. To quantify pathogen persistence, selected microbes were used to inoculate curly kale and intact tomato, which were then stored at either room (25°C) or refrigerated (4°C) temperatures for up to two weeks. Processing, as detailed above, occurred on days 0, 1, 3, 7, and 14. Data were analyzed in R Studio and modeled in Excel.
Results: Transfer rates were consistently higher to tomato than to kale (p<0.05) for both human pathogens. Intact bamboo, damaged bamboo, and damaged pressed paper all demonstrated consistently higher transfer rates to tomato than to kale (p<0.05). However, there was no significant difference found for intact pressed paper and stainless steel. There was also found to be no significant difference in the transfer of S. enterica and L. monocytogenes between surfaces and produce variant. Regarding retention rates, no significant difference was found when comparing any surface to the industry standard: stainless steel. Similarly, no difference was found, overall, with regards to damage or intact cutting boards. Pathogen persistence was not significantly different between produce variants at either room or refrigerated temperatures. However, overall survival and growth of pathogens was greater at room temperature than at refrigerated temperature (p<0.001). Neither S. enterica nor L. monocytogenes demonstrated significantly different persistence on either tomato or kale. However, overall growth of S. enterica was greater than L. monocytogenes (p<0.001). At room temperature, S. enterica showed significantly higher growth than L. monocytogenes (p<0.001), though, at refrigerated temperature, L. monocytogenes grew better than S. enterica (p<0.001).
Conclusion: Tomato poses a greater risk of cross-contamination than does kale. However, the cutting surface does not seem to significantly impact overall bacterial transfer. Therefore, in a domestic or commercial environment, cutting surface is not likely to significantly impact transfer, but produce is. Produce storage at refrigerated temperatures showed significant decrease of S. enterica growth and survival, but did not significantly deter growth of L. monocytogenes. These data indicate that, while proper storage of fresh produce is vital to deterring pathogenic growth, appropriate decontamination and cooking procedures are also necessary to decrease the risk of foodborne illness.