AN AUREOMYCIN-ROSE BENGAL AGAR FOR ENUMERATION OF YEAST AND MOLD IN COTTAGE CHEESE

Abstract

A peptone dextrose agar containing 20 ppm of aureomycin and 20 ppm of rose bengal was compared to acidified potato dextrose agar for the enumeration of yeast and mold. Mold and yeast isolates, as well as yeast and mold from Cottage cheese, were compared on the two agars. The results of the study showed no statistically significant difference between the mean counts on the agars and tests for bacterial growth of five species were all negative. The aureomycin-rose bengal agar had several advantages over the potato dextrose (PD) agar; spreading mold colonies were eliminated, there was no precipitation of casein to interfere with counting colonies, the possibility of some yeast and mold species not growing because of the low pH of the acidified PD medium was eliminated, and the red background aided in detecting colonies of yeast and mold.