Browsing by Author "Li, Yingying"
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Item Enhanced removal of Salmonella typhimurium and E. coli O157:H7 from blueberries and strawberries by solutions containing sodium dodecyl sulfate and organic acids or hydrogen peroxide(University of Delaware, 2013) Li, YingyingIncreasing consumption of raw blueberries has led to the need for improved food safety in the berry fruit industry. This study was undertaken to evaluate enhanced Salmonella and E. coli inactivation on blueberries by washing with sodium dodecyl sulfate (SDS) in combination with other common antimicrobial agents, such as organic acids and hydrogen peroxide. The addition of 5000 ppm SDS in 500 ppm acetic acid, 200 ppm hydrogen peroxide, and 20 ppm peroxyacetic acid resulted in more than 4.0 log10 CFU/g reductions of Salmonella and E. coli. Low-temperature frozen storage had a significant impact (P<0.05) on microbial counts of both treated and untreated blueberries. None of the washings decreased the total phenolic, anthocyanins content and apparent quality, but frozen storage caused significant damage to the texture of both treated and untreated blueberries. A solution containing 500 ppm acetic acid plus 5000 ppm SDS, 200 ppm hydrogen peroxide in combination with 5000 ppm SDS, and 20 ppm peroxyacetic acid coupled with 5000 ppm SDS holds promise in enhancing the safety of blueberries and frozen storage has the potential to enhance their effectiveness. However, these three washing solutions did not inactivate Salmonella and E. coli on strawberries presumably due to the rough surface of strawberries and the presence of numerous surface-borne achenes (seeds), which provide hidden areas for the bacteria to attach and are less accessible to sanitizing solutions. Thus, these experiments indicate that once strawberries were contaminated with Salmonella Typhimurium and E. coli O157:H7, there is a potential health hazard to cause illness for consumers.Item 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(Journal of Food Safety, 2021-12-28) Li, Yingying; Wu, ChangqingSalmonella 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.