Purpose: The purpose of this study was to determine the transfer of E. aerogenes from the surface of carrots and cucumbers to the flesh during the home peeling process.
Methods: A non-pathogenic nalidixic acid-resistant strain of E. aerogenes was grown overnight in tryptic soy broth at 37 °C, centrifuged and resuspended in sterile water. Fresh cucumbers and carrots were dipped in 200 ml of sterile water containing E. aerogenes for 15 min. Produce was allowed to dry for 15 min in a laminar flow hood. E. aerogenes was enumerated from the inoculum water, the removed peel and from the peeled produce using duplicate plates of MacConkey agar added with nalidixic acid. Counts were expressed as log CFU/g or ml and experiments were replicated.
Results: Counts of E. aerogenes in the water used to inoculate produce items were ~107CFU/ml. The mean counts of E. aerogenes in the removed peels of carrots and cucumber were 4.8 ± 0.2 and 3.8 ± 0.4 log CFU/g, respectively. It was observed that after peeling, internal parts of cucumber (mesocarp) and carrot (cortex) were contaminated with 2.6 ± 0.3 and 2.7 ± 0.4 log CFU/g, respectively. Contamination on the peeled flesh was likely due to transfer via the peeler blade during peeling.
Significance: Our results show that if the surfaces of cucumbers or carrots are contaminated with bacteria prior to peeling, the peeling process reduces but does not eliminate the presence of those same bacteria on the peeled flesh. These results may be helpful in understanding the risks posed by contaminated carrots or cucumbers.