Effects of pH and Water Activity on Microbiological Stability of Salad Dressing

Abstract

The water activity and pH of an experimental starch-based salad dressing were varied to evaluate inhibitory effects on microorganisms selected from groups known to be principal dressing spoilage agents. Dressing samples were inoculated with Lactobacillus fructivorans, Zygosaccharomyces bailii, or a yeast isolated from a spoiled commercial salad dressing. Both yeast and L. fructivorans displayed a minimum growth pH of approximately 3.55 to 3.60. The minimum aw observed was 0.89 for yeast growth and 0.91 for L. fructivorans. Combinations of aw and pH which imparted microbial stability without use of preservatives are described.