Efficacy of triple-wash using a peroxyacetic acid and hydrogen peroxide solution at reducing populations and cross-contamination of Salmonella Typhimurium and the surrogate Enterococcus faecium on tomatoes
Rebecca Stearns, Corey Coe, Ida Holásková, Kristen E. Matak, Annette Freshour, Jacek Jaczynski, Jingyi Xue, Yangchao Luo, Lisa Jones, Xinhao Wang, Cangliang Shen
Abstract
The efficacy of a triple-wash system to reduce and mitigate cross-contamination of Salmonella Typhimurium and Enterococcus faecium was tested on tomatoes. Tomatoes were dip-inoculated with S. Typhimurium or E. faecium followed by triple-washing for 45 s at each wash step: water + antimicrobial + water (WAW) or water + water + antimicrobial (WWA). A mixture [23 ml/dL hydrogen peroxide + 5.3 ml/dL peroxyacetic acid (SaniDate-5.0, SD)] was tested at 0, 0.0064, 0.1, and 0.25 ml/dL. Microbial population was estimated using a modified most-probable-number (MPN) method. Reductions of S. Typhimurium were similar (P > 0.05) to E. faecium (1.83–3.53 vs 1.72–3.65 log10MPN/g) with the greatest reductions at 0.25 ml/dL of SD. No differences (P > 0.05) were seen in reductions of S. Typhimurium or E. faecium regardless of wash strategy. Application of 0.25 ml/dL of SD in WAW or WWA wash strategy resulted in the lowest (P < 0.05) cell counts than the lower concentration treatments for S. Typhimurium (0.16–0.69 log10MPN/g) and E. faecium (−0.41 log10MPN/g). There were no differences (P > 0.05) in of survival between S. Typhimurium and E. faecium after treatment with the triple-wash strategies. Results suggest that E. faecium could be an acceptable surrogate for S. Typhimurium when validating antimicrobial washing systems on tomatoes.