Comparative performance of a mixed strain starter in cow's milk, ewe's milk and mixtures of these milks

The acidification ability of a mixed strain starter consisting of Lactococcus lactis ssp. lactis IPLA 947, L. lactis ssp. lactis biovar. diacetylactis IPLA 838 and Leuconostoc citreum IPLA 616 and designed for Afuega'l Pitu cheese manufacture from pasteurized milk was assayed in cow's and ewe's milk, and in mixtures containing 10% and 20% ewe's milk in cow's milk. The evolution of microbial counts, pH, titratable acidity, organic acids and volatile compounds production throughout the incubation period was determined. The use of ewe's milk as a culture medium increased the metabolic activity of the starter culture reflected in a higher lactose consumption, significantly higher acidity and some carbon source-derived organic acids and volatile compounds production, as well as in slightly higher starter strains growth, although the latter was not statistically significant. Thus, it is suggested that ewe's milk or mixtures of ewe's with cow's milk can be satisfactorily used in the manufacture of this traditional cheese.