engleski

Secondary metabolites produced by yeast strains isolated from Cabernet Sauvignon and Chardonnay grapes

For many years it has been standard practice in winemaking to use pure cultures of oenologically suitable species, in particular Saccharomyces cerevisiae and its physiological variants. Positive properties of some non-Saccharomyces yeasts could be also used in wine production. Various strains, producing different amounts of secondary metabolites, can impart desirable or undesirable flavour determinants to the wine, thereby affecting the ultimate product quality. The use of a single strain for different types of wines is not appropriate, due to a potential uniformity of aromatic characteristics in the final products. It is presumed more advantageous to use natural autochthonous strains, with desirable technological characteristics and a metabolic profile corresponding to each wine. Local selected yeasts is believed to be much more effective and competitive because they are better acclimated to the environmental conditions. Although the use of must as a fermentation medium is a common practice to study and compare different yeast strains, its use is limited throughout the whole year. Variations in composition of must can be significant regarding geographical and climate differences. In this work a new standard and easy available medium was selected. Microfermentations of the standard medium were done at 12 and 20^o C using different yeasts: ZIM 1900 (identified as Saccharomyces cerevisiae, previously isolated from Cabernet Sauvignon grapes) ZIM 1899 (isolated from Chardonnay grapes and identified as Torulaspora delbrueckii, which was classified before as Saccharomyces rosei), Saccharomyces bayanus strain Z-2 (Collection of microorganisms of Faculty of Food Technology and Biotechnology, Zagreb, Croatia) and two commercial strains of wine yeast, strain A and strain B. Contents of some volatile aroma compounds (acetaldehyde, diacetyl, isoamyl alcohol, ethyl acetate, ethyl propionate, ethyl hexanoate, ethyl octanoate, ethyl lactate and isoamyl acetate) produced at two different temperatures during microfermentations of synthetic medium were determined by gas chromatography. Differences in aroma volatile compounds produced by fermentation with different yeast strains at different temperatures were observed.

Secondary metabolites; Wine Yeast; Cabernet Sauvignon; Chardonnay

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