Survival of Salmonella Typhimurium and Escherichia coli O157:H7 on blueberries and impacts on berry quality during 12 weeks of frozen storage after washing with combinations of sodium dodecyl sulfate and organic acids or hydrogen peroxide

Salmonella spp. and Escherichia coli are well tolerant of freezing. This study was to investigate survival of the foodborne pathogens during storage at −18 ± 2°C for 12 weeks on blueberries after washing with: 500 ppm acetic acid plus 5,000 ppm sodium dodecyl sulfate (SDS) (AA/SDS), 20 ppm peroxyacetic acid plus 5,000 ppm SDS (PPA/SDS), or 200 ppm hydrogen peroxide plus 5,000 ppm SDS (H2O2/SDS), when compared with findings from no wash, or wash with water, 80 ppm PPA or 200 ppm chlorinated water. Following a 60 s contact with one of the three new solutions, the treatments showed 3.3–3.9 log10 CFU/g reductions in Salmonella Typhimurium and E. coli O157:H7 counts. After 2 weeks of frozen storage, 3.9–4.2 log10 CFU/g reductions of Salmonella and E. coli were observed. After 12 weeks of frozen storage, Salmonella and E. coli survivors were below detection limits (0.39 log10 CFU/g) in berries washed with new solutions. The frozen storage had a significant impact (p < .05) on microbial counts of both treated and nontreated blueberries. Although none of these washings decreased the total phenolic and anthocyanins contents and apparent quality at time 0, frozen storage caused significant damage on the texture of both treated and nontreated blueberries. Interestingly, no significant decrease in the total phenolic, anthocyanins content, and apparent quality was observed during the 12-week frozen storage. The counts of total bacteria, yeasts, and molds decreased throughout storage for treated and untreated berries. This demonstrates that the three wash solutions enhance the safety of frozen berries.

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