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.