Advances in the development of a methodology to identify common yeast contaminants of high sugar food products

Sixty-eight strains belonging to seven yeast species isolated in our labora tory from high sugar foods (Debaryomyces hansenii, Issatchenkia orientalis, Saccharomyces cerevisiae, Torulaspora delbrueckii, Zygosaccharomyces baili i, Zygosaccharomyces rouxii), mere studied in order to provide small indust ries with simple and vapid methods for detecting contaminations. Different strategies were used based on (i) the design of selective/differential cult ure media by adding to a basal medium for yeasts inhibitory agents, dyes or chromogenic substrates, and (ii) the detection of specific enzymatic activ ities. The mentioned yeast species could be differentiated on the basis of their growth oil three isolation media (eosin/methylen blue, acetic acid, a nd acetic acid/potassium tellurite) and the use of an additional test for d iscrimination (growth on 2-keto-D-gluconate, and beta-glucosidase or alkali ne phosphatase activities).