Yeasts associated with Sardinian ewe's dairy products

Area of Science:

• Food Microbiology
• Dairy Science
• Mycology

Background:

• Yeasts play a significant role in the ripening and flavor development of cheese.
• Understanding yeast populations in traditional cheeses is crucial for quality control and product development.

Purpose of the Study:

• To investigate the occurrence and diversity of yeasts in Sardinian ewe's cheeses.
• To characterize the biochemical and technological properties of isolated yeast strains.

Main Methods:

• Analysis of 160 cheese samples (pecorino, caciotta, feta, ricotta).
• Isolation and identification of yeast strains using standard microbiological techniques.
• Assessment of proteolytic and lipolytic activities, growth under various conditions (temperature, salt), and substrate assimilation/fermentation.

Main Results:

• 76.2% of samples yielded yeast growth, with highest counts in caciotta and feta.
• 281 strains from 16 genera and 25 species were identified, with Debaryomyces hansenii being dominant.
• Key species like Kluyveromyces lactis and K. marxianus assimilated lactose, while many assimilated lactic acid. Citrate assimilation was noted in D. hansenii.
• Most yeasts showed weak proteolytic activity but varied lipolytic activity. Strains exhibited tolerance to low temperatures and some to high salt concentrations.

Conclusions:

• Sardinian ewe's cheeses harbor a diverse yeast population with varied metabolic capabilities.
• Debaryomyces hansenii, Kluyveromyces lactis, and K. marxianus are significant yeast species in these cheeses.
• The identified yeasts possess traits relevant to cheese ripening and potential technological applications.