INHIBITION OF THE GROWTH OF YEASTS IN FERMENTED SALADS

Salads composed of vegetables and/or meat in an oil-in-water emulsion were prepared by fermentation for 7 h at 42-degrees-C or 45-degrees-C with strains of Lactobacillus spp. Their stability towards spoilage yeasts was studied using Saccharomyces cerevisiae, Saccharomyces exiguus and Torulaspora delbrueckii, isolated from salads, as well as Pichia membranaefaciens and Zygosaccharomyces bailii. Salads fermented with good lactic starters usually had pH values of less-than-or-equal-to 4.2 and lactic acid concentrations of 0.28 to 0.43% (w/w). High numbers of spoilage yeasts (and production of large volumes of CO2) were not attained in these salads, provided the initial concentration of spoilage yeasts was sufficiently low (less-than-or-equal-to 100 CFU/g). Inhibition of spoilage yeasts in lactic fermented salads is probably due to lactic acid, the low storage temperature and the low residual oxygen concentration.