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

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University of Delaware
Increasing 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.