Postharvest control of Escherichia coli O157:H7 on romaine lettuce using a novel pelargonic acid sanitizer

Authors: CIMOWSKY, SAMUEL - University Of Georgia; DEV KUMAR, GOVINDARAJ - University Of Georgia; RIBEIRO DA SILVA, ANDRE LUIZ - Auburn University; WHITE, ELIZABETH - University Of Georgia; KERR, WILLIAM - University Of Georgia; RODRIGUES, CAMILA - Auburn University; Juneja, Vijay; DUNN, LAUREL - University Of Georgia

Submitted to: LWT - Food Science and Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/14/2021
Publication Date: 7/17/2021
Citation: Cimowsky, S., Dev Kumar, G., Ribeiro Da Silva, A.B., White, E., Kerr, W.L., Rodrigues, C., Juneja, V.K., Dunn, L.L. 2021. Postharvest control of Escherichia coli O157:H7 on romaine lettuce using a novel pelargonic acid sanitizer. LWT - Food Science and Technology. 112168. https://doi.org/10.1016/j.lwt.2021.112168.
DOI: https://doi.org/10.1016/j.lwt.2021.112168

Interpretive Summary: Romaine lettuce continues to be linked to several large, multistate Escherichia coli O157:H7 outbreaks, with thousands of reported illnesses, making it a commodity of significant food safety concern. We examined the efficacy of a novel pelargonic acid (Pel) emulsion in a model wash system on E. coli O157:H7 reduction on inoculated romaine lettuce. Our results suggest that the Pel emulsion effectively reduce E. coli O157:H7 attached on the surface of romaine lettuce and reduce cross-contamination to clean leaves when compared to water alone in a simulated wash system. The antimicrobial action of Pel against E. coli O157:H7 makes it a promising active ingredient in sanitizing or disinfecting agents and will be useful to the produce industry as well as regulatory agencies to aid in ensuring the safety of romaine lettuce.

Technical Abstract: Chlorine and peroxyacetic acid (PAA) can reduce bacterial cross-contamination in produce wash tanks but do not demonstrate the same antimicrobial activity against bacteria attached to the produce surface. A novel pelargonic acid (Pel) emulsion was examined for its ability to reduce Escherichia coli O157:H7 attached to the surface of inoculated romaine lettuce, and for its ability to limit E. coli O157:H7 cross-contamination to clean romaine lettuce leaves within a model wash system. The Pel emulsion was tested at concentrations of 7.5, 30 and 50 mM and compared to 80 ppm PAA, 200 ppm free chlorine (hypochlorous acid), sterile deionized water, and a no-rinse treatment. Efficacy of all sanitizer-containing treatments was also examined after supplementing the wash solution with 0.5% w/v romaine lettuce puree to examine the impact of organic matter. Sanitizer efficacy and impact on lettuce quality over time were examined by washing inoculated lettuce and storing for 7 days at 4C. Overall, Pel emulsion at 30 and 50 mM significantly reduced E. coli O157:H7 by about 0.6 log CFU/g immediately post-wash compared to all other treatments. The Pel at 30 and 50 mM also performed significantly better than all wash treatments after 24 h and 7 d storage, resulting in E. coli O157:H7 reductions from inoculated leaves close to the limit of detection (1.0 log CFU/g) by 7 days. Compared to the sterile deionized water treatment (4.9 log CFU/g at 0 h), all sanitizer treatments effectively limited cross-contamination to uninoculated lettuce leaves by more than 3 log CFU/g, regardless of time interval or the presence of organic load. However, Pel did exert phytotoxic activity on lettuce leaves at the levels tested, so reformulation for produce washing or alternative applications such as non-food contact surface sanitation may be more appropriate. Nevertheless, because Pel are effective biocides, incorporation into films or packaging materials may be a means to employ their preservative qualities while minimizing phytotoxic damage.