Evaluation of the efficacy of a mixer of hydrogen peroxide and peroxyacetic acid to mitigate microbial cross-contamination of Salmonella Typhimurium and the surrogate Enterococcus faecium during triple-washing of butternut squash
Jesica Temple, Rebecca Stearns, Corey Coe, Heather Chaney, Janet C. Tou, Annette Freshour, Yangchao Luo, Cangliang Shen
Abstract
This study evaluated the effectiveness of triple washing with a hydrogen peroxide (H2O2)-peroxyacetic acid (PAA) mixer to mitigate microbial cross-contamination of Salmonella Typhimurium and the surrogate bacteria Enterococcus faecium on butternut squash. To produce cross-contamination, one or two butternut squash were dip-inoculated with nalidixic acid-resistant S. Typhimurium (4.03 log10MPN/g) or E. faecium (4.20 log10MPN/g) and then mixed with 6 (“1:6”) or 5 (“2:5”) uninoculated fresh clean squash followed by triple washing for 45 s in water, water, and then the H2O2-PAA mixer at doses 0, 0.0064, 0.25, 0.50, and 0.84 ml/dL. The most-probable-number was used to determine microbial population. Triple-washing squash with 0.25–0.84 ml/dL H2O2-PAA mixer resulted in greater (P < 0.05) reductions of S. Typhimurium and E. faecium by 2.50–3.10 and 2.01 to 3.43 log10MPN/g, respectively, than the 0 and 0.0064 ml/dL treated samples. Applying 0.25–0.84 ml/dL H2O2-PAA mixer resulted 1.02 to 1.31 and 0.84 to 1.12 log10MPN/g cross-contaminated S. Typhimurium cell counts in the “1:6” and “2:5” ratio tests, respectively. E. faecium showed similar reduced cell counts and cross-contaminated cell counts in most tested treatments compared to S. Typhimurium, indicating it is an appropriate surrogate bacterium for Salmonella during post-harvest produce washing challenge studies.