P3-60 A Blend of Benzalkonium Chloride, Acetic Acid, and Methyl Paraben Effectively Reduces Escherichia coli O157:H7, Salmonella spp., and Listeria monocytogenes in Produce Wash Water, But Lacks Consistent Efficacy on Romaine and Iceberg Lettuce

Wednesday, July 12, 2017
Exhibit Hall (Tampa Convention Center)
Nicholas Sevart , Kansas State University , Manhattan , KS
Sara Gragg , Kansas State University , Olathe , KS
Matthew Krug , Kansas State University , Manhattan , KS
Jacob Jenott , Kansas State University , Olathe , KS
Randall Phebus , Kansas State University , Manhattan , KS
Introduction:  Illnesses associated with fresh produce demonstrates the need for effective intervention techniques. Improving the sanitizing efficacy of postharvest washes is a critical goal for improving fresh produce safety; however, contamination is difficult to address in fresh-cut produce such as lettuce.

Purpose:  Efficacy of a proprietary blend of benzalkonium chloride, acetic acid and methyl paraben (BAM) was evaluated as a wash to reduce Listeria monocytogenes, Salmonella, and Escherichia coli O157:H7 on fresh-cut romaine and iceberg lettuce. Products were subjected to concentration/time combinations of the BAM wash and pathogen survival on product and resultant wash water was determined.

Methods:  Freshly chopped romaine and iceberg lettuce was mist inoculated with L. monocytogenes, Salmonella, or E. coli O157:H7 (~ seven log CFU/g) and allowed to attach for 30 minutes. Lettuce was submerged with agitation in a 0, 1, 2 or 3% wash for one or five minutes, rinsed for one minute in tap water, and dewatered. Lettuce and wash water samples were homogenized in D/E Neutralizing Broth, and serial dilutions were spread plated using an injury-recovery agar overlay protocol to enumerate surviving L. monocytogenes, Salmonella, and E. coli O157:H7 levels.

Results:  All BAM-containing wash waters harbored less (P≤0.05) pathogenic contamination than the 0% control treatment. Concentration, contact time, and their interaction were not significant (P>0.05) for all pathogens on iceberg or romaine, with the exception of concentration (P=0.0021) for E. coli O157:H7-inoculated romaine. The 3% wash removed 0.66 log CFU/g more E. coli O157:H7 than 0% on the romaine lettuce.

Significance:  Controlling pathogenic contamination in postharvest produce wash water is critical for preventing cross-contamination during commercial washing operations. The proprietary BAM wash was effective as a wash water sanitizing agent. Because pathogen reduction was lacking on fresh-cut lettuce, likely due to internalization of the inoculum within the lettuce tissue during washing, future studies should investigate efficacy on other products.