A chromogenic medium for the detection of yeasts with beta-galactosidase and beta-glucosidase activities from intermediate moisture foods

A selective and differential solid medium for the specific detection of som e common yeasts frequently causing spoilage in intermediate moisture foods is described. The principle of the method is based on the detection of two enzymes, beta-glucosidase and beta-galactosidase, using the chromogenic sub strates salmon-Glue and X-Gal. Over 140 yeasts and bacteria were tested, an d Debaryomyces hansenii and Kluyveromyces marxianus strains produced salmon and dark blue colonies, respectively, thus permitting their clear discrimi nation from other yeasts common in intermediate moisture foods. The medium was very satisfactory when intermediate moisture foods were tested.