Abstract
Two rare moulds, Helicostylum pulchrum and Scopulariopsis flava, were isolated from a brown stain found on the cut surface of commercially available Brie cheese. Spoilage yeast Debaryomyces hansenii was also present in the same portion. H. pulchrum is psychrophilic but not commonly found as spoilage mycobiota on natural cheese. It grew rapidly on malt extract agar or Brie cheese at 10°C, while D. hansenii and S. flava developed at a moderate and quite slow rate, respectively, under the same condition. To examine the relationship between the contaminants and a discoloration, fungal spike trials were carried out. A reddish or yellowish discoloration was found on the spiked cheese slices by the inoculum of D. hansenii alone or D. hansenii combined with H. pulchrum or/and S. flava. It was not pigments produced by spiked species, but caused by lactic acid bacteria. Concerning H. pulchrum- or D. hansenii-damaged cheeses, cytotoxic assay was done using human neuroblastoma cells. The extracts of these damaged cheeses exhibited no toxicity to the human cells.
