UH-53 Contaminated Convenience: Does method of grocery procurement affect microbial burden of ground beef

Since the COVID-19 pandemic, access to grocery delivery has expanded substantially, unlocking a greater concern surrounding foodborne illnesses and their risks. To evaluate these concerns, we assessed three methods of obtaining groceries; in-store shopping, grocery delivery, and meal kit delivery services, to determine if procurement method affects total microbial load or Escherichia coli counts in ground beef. Testing was performed on 21 samples of 80/20 beef obtained via in-store shopping, 22 samples obtained via grocery delivery, and 20 samples obtained via meal kit delivery. Samples were homogenized and plated on trypticase soy agar (TSA), MacConkey agar (MAC), and Chromagar plates (CA). The plates were incubated at 37°C for 48 hours. Store-bought samples yielded the highest average colony counts on TSA at 1.02 x 106 CFUs/g. Meal kit samples resulted with the second highest colony count on TSA plates at 7.63 x 105 CFUs/g and grocery delivery samples had 7.49 x 105 CFUs/g. When comparing the bacterial growth on MAC, store bought samples have the highest CFUs/g at 2.27 x 105. Grocery delivery samples resulted in 8.34 x 103 CFUs/g with meal kit samples close behind at 7.04 x 103 CFUs/g. This represents 27 times less gram-negative bacteria from grocery-delivery samples and 32 times less from meal kit samples when compared to store-bought samples. Chromagar was used to selectively identify E. coli O157, which forms pink colonies. Three store-bought samples, two grocery delivery samples, and one meal kit sample had presumptive E. coli O157 colonies. All presumptive samples were tested using agglutination to confirm the presence of E. coli O157. Of these, only the meal kit sample was confirmed positive. The FDA has established critical threshold values of 1x105 CFUs/g for total microbial count and 1x103 CFUs/g for coliforms as an acceptable limit for ground beef (Vial et al., 2019). Results from our study showed 52.4%, 50%, and 22.2% of in-store shopping, grocery delivery, and meal kit samples respectively had total microbial counts higher than the acceptable threshold, while 44.4%, 57.9%, and 35% of store-bought, grocery-delivery, and meal kit samples had total coliform counts over the acceptable threshold. Overall trends indicate that procurement method does influence total microbial loads of ground beef, revealing that delivery methods have lower microbial loads; however, these findings were not statistically significant due to high variance between all sample types. There is still a chance of high microbial loads regardless of the procurement method.