Detection and identification of yeasts in natural whey starter for Parmigiano Reggiano cheese-making

The yeast populations of natural whey starter (NWS) samples from dairies of PDO Parmigiano Reggiano cheese production area were enumerated and characterised. Yeasts were detected with an average value higher than 3 log cfu mL−1 and in a case study we highlighted the correlation between the yeast growth and incorrect management of NWS fermentation. Isolated strains showed the typical Kluyveromyces marxianus PCR-RFLP pattern and D1/D2 sequences obtained displayed similarity values ranging from 99% to 100% for the same species. RAPD-PCR fingerprinting revealed 14 biotypes. The ability of several strains to grow at 52 °C demonstrates that the yeasts may be perfectly integrated into the ecosystem of NWS. This work confirms that yeasts are part of the NWS secondary microbiota, composed by wild strains with relevant biotechnological interest.