Evaluation of Media for Enumerating Yeasts and Molds in Fresh and Frozen Fruit Purees

Abstract

Five mycological media were evaluated for their suitability to enumerate yeasts and molds in 11 different fresh and frozen fruit purees. Overall, acidified (pH 3.5) potato dextrose agar (PDA) and oxytetracycline-glucose-yeast extract (OGY, pH 6.5) agar supported highest overall recovery of total fungal populations from purees; plate count agar supplemented with antibiotics and rose bengal-chlortetracycline agar (RBC) were inferior. Dichloran-rose bengal-chloramphenicol agar was superior for restricting spreading of molds, thus facilitating enumeration of colonies. RBC agar was superior to PDA for recovering molds; PDA was superior to RBC for detecting yeasts. It is concluded that selection of acidified PDA and OGY in lieu of other mycological media is appropriate when high-acid food materials such as fruit purees are analyzed for total fungal populations. These media would be exceptionally desirable when test products contain low populations of molds and high populations of yeasts.