Reduction in Resident Microflora, and Experimentally Inoculated Salmonella enterica, on Spinach Leaves Treated with Vinegar and Canola Oil

Abstract

In this study, we explored the use of vinegar, or vinegar and canola oil as a salad dressing, to reduce bacterial levels on spinach leaves. We found that incubation of spinach leaves with various types of vinegar substantially reduced the predominantly gram-negative microflora. A similar response was observed when spinach leaves were incubated with white vinegar mixed in various proportions with canola oil, as used in salad dressing. We assessed the effects of vinegar, or vinegar and oil, on spinach leaves that had been experimentally inoculated with a cocktail of Salmonella enterica strains. Allowing the mixture to sit at room temperature for at least 20 min resulted in a substantial reduction (up to 2.0 log CFU) in numbers of S. enterica. Vinegar and oil caused a limited reduction in CFU (0.5 log) for spinach leaves experimentally inoculated with a cocktail of Listeria monocytogenes strains. These findings suggest that mixing spinach leaves with vinegar and oil as a salad dressing can reduce the bacterial load associated with the spinach leaves, including Salmonella if it is present.