Occurrence and involvement of yeast biota in ripening of Italian Fossa cheese

A microbiological investigation on a typical Italian Fossa cheese during ripening was reported here. Two yeast isolation campaigns were conducted to investigate the yeast diversity on cheese and pit environment, before and at the end of cheese ripening in pit, using classical and molecular tools. Before the ripening, eight different yeast species were identified from pit environment: Candida zeylanoides, Candida norvegica, Pichia occidentalis, Pichia guilliermondii, Pichia jadinii, Cryptococcus albidus, Cryptococcus skinneri, and Sporobolomyces roseus. Only C. zeylanoides was also found at the end of the cheese-ripening stage, together with the new isolated species Wickerhamomyces anomalus, Saccharomyces cerevisiae, Debaryomyces hansenii, and Candida homilentoma. To evaluate the contributions of these autochthonous species found during ripening, they were inoculated into fresh cheeses. Results show that D. hansenii, C. zeylanoides, and W. anomalus drastically reduced the colonization of molds on the cheese surface, with excellent results of sensory evaluation of the ripened cheese. The cheese inoculated with these indigenous selected yeasts did not show any defects, and volatile organic compounds analysis showed a high concentration of methyl ketones, and butanoic, hexanoic, and octanoic acids, which typically enhance the taste of the highly matured Fossa cheese. These results highlight the positive role of these indigenous yeasts during ripening process of the Fossa cheese.