The purpose of this study was to examine three yeast strains: Candida kefyr PII1b, Candida sphaerica FII7a and Yarrowia lipolytica JII1c, isolated from Polish mould cheese Rokpol as potential cheese adjunct cultures. The strains were introduced aseptically to cow, goat and sheep milk and the effect of their hydrolytic enzymes on the milk components degradation was evaluated during yeast growth. Inoculated milk samples were incubated at room temperature for 12 days. During that time yeast growth in milk was monitored. The pH and level of nitrogen soluble at pH 4.6 were also determined. After 12 days of milk incubation with yeasts concentration of organic acids and the level of protein and lipid degradation were evaluated. The control were bovine, caprine and ovine milk samples incubated without yeasts. It was shown that Candida kefyr PII1b and Candida sphaerica FII7a exhibited better growth in each kind of milk than Y. lipolytica JII1c. The population of two former yeast strains reached the level of 107-108 cfu mL-1, whereas the population of Y. lipolytica was about one logarithmic cycle lower. The growth of Y. lipolytica JII1c in every milk sample was accompanied with utilization of citric acid. In the milk samples inoculated with Candida kefyr PII1b and Candida sphaerica FII7a insignificant increase of acetic, lactic and propionic acids concentration was observed. The highest rate of milk proteins degradation was caused by Y. lipolytica JII1c. This strain exhibited also the highest lipolytic activity against fat, causing significant release of short – and medium- chain fatty acids especially butyric and caprice acids as well as two longchain fatty acids as palmitic and oleic. Yeast Y. lipolytica JII1c is the most promising adjunct culture for soft cheese production from each kind of milk.

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