A Modified Rose Bengal Medium for the Enumeration of Yeasts and Moulds from Foods

摘要

Yeasts and moulds from 44 food samples were selectively enumerated on RBCC (Cooke's Rose Bengal/chlortetracycline/chloramphenicol) and OGY media (oxytetracycline/glucose/yeast agar). In regard to bacterial growth control, a combination of the two antibiotics proved to be superior to one. In tests with 18 mould and 14 yeast strains, the optimum inhibitory action of Rose Bengal was found to be at a concentration of 150 mg/l RBCC. Mould and yeast counts of 62 samples determined on RBCC - using increasing Rose Bengal concentrations up to 150 mg/l - and OGY media showed no difference; only the yeast count of samples of vegetables and meat, determined on RBCC medium containing 150 mg Rose Bengal per litre, showed a slight decrease. Application of the modified Rose Bengal medium enables an adequate control of bacterial growth and restricts mould colony size, facilitating a more rapid and accurate enumeration. This also holds for yeast colonies, which, in the absence of Rose Bengal, are very often covered by the mould colonies.