Yeasts as adjunct starters in matured Cheddar cheese.

Debaryomyces hansenii and Yarrowia lipolytica are typical foodborne yeast species frequently associated with dairy products and capable of predominating the yeast composition in such systems. The two species fulfil a number of criteria to be regarded as co-starters for cheesemaking. They are known for their proteolytic and lipolytic activity as well as their compatibility and stimulating action with the lactic acid starter cultures when co-inoculated. Recent studies indicated that yeasts could be included as part of starter cultures for the manufacturing of cheese, enhancing flavour development during the maturation. The potential of D. hansenii and Y. lipolytica as agents for accelerated ripening of matured Cheddar cheese has been evaluated during four cheese treatments. The interaction between the two yeast species and the lactic acid bacteria was surveyed incorporating (i) D. hansenii, (ii) Y. lipolytica, (iii) both species as adjuncts to the starter culture and (iv) a control cheese without any additions for the production of matured Cheddar cheese. The physical and chemical properties of the cheeses were monitored in order to evaluate the contribution of the yeasts to cheese maturation. The yeasts grew in association with the lactic acid bacteria without any inhibition. The yeasts species when individually added contributed to the development of bitter flavours despite accelerated development of strong Cheddar flavours. When both species were incorporated as part of the starter culture, the cheese, however, had a good strong flavour after a reduced ripening period. The cheese retained this good flavour and aroma after 9 months of production. The simultaneous application of D. hansenii and Y. lipolytica as part of the starter culture for the production of matured Cheddar cheese is proposed.