engleski

The use of Candida stellata in combination with Saccharomyces cerevisiae or S.paradoxus for glycerol production during fermentation

Glycerol is quantitatively the most important by-product of the alcoholic fermentation after ethanol and carbon dioxide, plays major role in balancing the NADH/NAD intracellular ratio and in combating osmotic stress.It is a non-volatile compound which has non aromatic properties, but which significantly contributes to wine quality by providing sweetness and fullness.Wine fermentations were conducted by naturally occurring or selected wine yeast strains of Saccharomyces cerevisiae or S.bayanus.However, S.paradoxus is recognized as a possible novel starter culture in wine fermentation.During the naturally occurring fermentation, non Saccharomyces species are involved in the aroma formation, especially in the initial stages and Candida stellata is a common non-Saccharomyces yeast.C.stellata exhibits a peculiar fermentation behaviour characterized by a very low fermentation rate and high production of secondary compounds such as glycerol, acetoin, acetaldehyde and succinic acid.The aim of this investigation was to determinate how different yeast species and their combinations (S.cerevisiae, S.paradoxus, C.stellata, S.cerevisiae and C.stellata, S.paradoxus and C.stellata)influence the concentration of glycerol in a laboratory wine fermentation.We used two different nitrogen concentration in a synthetic must and different ratio of glucose and fructose.After the alcoholic fermentation yeast growth rate, alcohol, residual sugar, volatile acidity and concentration of glycerol was analysed.All the investigated yeast strain and yeast combinations finished the fermentation except for the C.stellata fermentation.The glycerol synthesis was affected by yeast species.In the case of S.paradoxus fermentation the higher concentration of glycerol was determined.Synthesis of glycerol was affected by the concentration of amino acids only in the case of S.paradoxus fermentation and the combination of S.paradoxus and C.stellata.Glycerol synthesis was non affected by investigated factors in the case of S.cerevisiae.Surprisingly, the higher concentration of glycerol in C.stellata fermentation, was detected in the must with low concentration of amino acids and higher concentration of fructose.

Candida stellata; Saccharomyces cerevisiae; Saccharomyces paradoxus; glycerol; fermentation

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