Microbiological spoilage of mayonnaise and salad dressings.

Saccharomyces bailii was isolated from two-thirds of the spoiled mayonnaise and salad dressing samples examined. Most of the rest were spoiled by Lactobacillus fructivorans. However, one sample contained large numbers of both S. bailii and L. plantarum. Two of the spoiled samples also contained small numbers of bacilli. Bacillus subtilis, B. pumilis, B. polymyxa, B. megaterium, and B. licheniformis were found in one sample and B. subtilis and B. pumilis in another. Small numbers of B. subtilis and B. licheniformis were also present in one unspoiled sample. Several media were evaluated for the isolation of L. fructivorans. S. bailii and L. fructivorans vigorously fermented glucose. The concentration of glucose in the spoiled samples ranged from 0 to 38.5 g/kg and from 1.3 to 17.8 g/kg for the unspoiled samples.