Comparing the Efficacy of Two Triple-Wash Procedures With Sodium Hypochlorite, a Lactic–Citric Acid Blend, and a Mix of Peroxyacetic Acid and Hydrogen Peroxide to Inactivate Salmonella, Listeria monocytogenes, and Surrogate Enterococcus faecium on Cucumbers and Tomatoes

Abstract

This study was designed to evaluate two triple-wash procedures with commercial antimicrobials to inactivate foodborne pathogens and surrogate bacteria on cucumbers and tomatoes. Fresh, West Virginia locally grown cucumbers and tomatoes were dip-inoculated with Salmonella Typhimurium and Tennessee, Listeria monocytogenes (3-strain), and Enterococcus faecium. Produce was washed through two triple-wash steps (10 s each) including water dip, antimicrobial dip, and water dip (WAW), or water dip, water dip, and antimicrobial dip (WWA), followed by draining (2 min) on aluminum foil. A triple-water (WWW) process was also included as a water-only control. Tested treatments were (1) water; (2) sodium hypochlorite (SH, 100 ppm, pH 8.2); (3) acidified sodium hypochlorite (ASH, 100 ppm, pH 6.8 adjusted by citric acid); (4) lactic and citric acid blend (LCA, 2.5%); and (5) a H 2 O 2-peroxyacetic acid mix [SaniDate-5.0 (SD) 0.0064, 0.25, and 0.50%]. Surviving bacteria were recovered on xylose lysine tergitol-4 (XLT-4, Salmonella), Modified Oxford (MOX, L. monocytogenes), and bile esculin agar (E. faecium). Data (two replicates, four samples/replicate) were analyzed using the mixed model procedure of SAS (P = 0.05). Counts of Salmonella, L. monocytogenes, and E. faecium on unwashed cucumbers and tomatoes were 5.42-6.23, 6.31-6.92, and 6.05 log colony-forming units (CFU)/produce, respectively. Triple-wash with water only reduced all three tested bacteria by 0.45-1.36 log CFU/fruit. Triple-wash by WWA with antimicrobials achieved additional reductions [least squares means (LsMeans)] of 0.38 log CFU/cucumber (Salmonella), 0.56 log CFU/cucumber (E. faecium), 1.48 log CFU/tomato (Salmonella), 1.09 log CFU/tomato (L. monocytogenes), and 0.71 log CFU/tomato more than the WAW procedure. Applying SD-0.25 and SD-0.50% solutions Li et al. Triple-Wash on Cucumbers and Tomatoes in triple-washing cucumbers and tomatoes resulted in reductions (P > 0.05) similar to ASH and greater reductions (P < 0.05) than SH and LCA. E. faecium was less susceptible (P < 0.05) or there was no difference (P > 0.05) in comparison with Salmonella in most cases, except for tomatoes treated with WWA. The results of this study indicate that SD could be used as an alternative antimicrobial agent for chlorine water in triple-wash processing at local small produce plants. Future pilot plant validation studies and cost-effectiveness analyses are needed for applying SD solutions in triple-wash by WV local small produce growers.

Evaluation of the Effectiveness of Aeration and Chlorination during Washing to Reduce E. coli O157:H7, Salmonella enterica, and L. innocua on Cucumbers and Bell Peppers

“…The inoculated cucumbers had a relatively smooth surface and did not have a stem or calyx section; this potentially indicates that the use of a sanitizer with or without bubbles may be sufficient to remove L. innocua from the surface of this produce. A previous study reported that 100 ppm of chlorinated water was effective in reducing the population of L. monocytogenes in cucumbers and tomatoes [ 36 ]. Another study involving the intentional introduction of bacteria to fresh tomatoes revealed that immersing them in a 200 ppm chlorine solution for 15 min led to an 8.06 log reduction of E. coli from the tomato surfaces, while dipping lettuce leaves in a 100 ppm chlorine solution resulted in a 3.00 log reduction of Salmonella spp.…”

“…This is consistent with the results of a study by Li et al, (2020) that compared the efficacy of different washing procedures on cucumber and tomatoes. Findings from this study suggested that the antimicrobial efficacy of chlorinated water at a concentration of 100 ppm significantly removed Salmonella spp., regardless of the produce type [ 36 ].…”

Exploring Peracetic Acid and Acidic pH Tolerance of Antibiotic-Resistant Non-Typhoidal Salmonella and Enterococcus faecium from Diverse Epidemiological and Genetic Backgrounds

“…Our analysis of Efm from all sources revealed no significant association between MIC PAA and minimum growth pH or between MBC PAA and minimum survival pH (p > 0.05) (Figure 7). (e) (f) As far as we know, there are limited studies showing the susceptibility of Efm populations to PAA, and they use diverse methodological strategies [40,55,56], which makes it difficult to compare our data with isolates from other collections. However, this study shows that Efm can survive above the minimum concentration of PAA used in the food chain (20 mg/L sanitation of automatic spraying in closed systems; 125 mg/L hand disinfection) and in the clinical settings (125 mg/L hand disinfection in hospitals, health and animal care areas) [8].…”