engleski

Influence of yeasts on high sugar must fermentation of cv. Plavac mali in production of traditional sweet wine Prošek

Today there are numerous dessert (sweet) wines produced all over the world and they are given different names, usually characteristic of the areas they come from. In the winegrowing regions of coastal Croatia the production of dessert sweet wine Prošek has become traditional. In this experiment, dried grapes of Plavac mali variety from vine-growing location of Pelješac were used. Process of alcoholic fermentation done by autochthonous yeasts and two types of selected osmophilic yeasts Saccharomyces cerevisiae var. uvarum and Saccharomyces cerevisiae var. bayanus was monitored. In previous research it had been shown that Saccharomyces cerevisiae var. uvarum and Saccharomyces cerevisiae var. bayanus can carry out alcoholic fermentation at low temperatures and thus create low ratio of volatile acids. Therefore, the purpose of this work is to investigate the influence of yeasts on the production of some products of alcoholic fermentation. Concentration of reducing sugars in must at the beginning of fermentation was 344.3 g/L, and glucose/fructose ratio was 1.33. In all the experiments the yeasts fermented glucose first, while the fermentation of fructose took longer and it was mostly the remaining sugar in the final product. The yeasts influenced the glucose/fructose ratio, which was the lowest when using Saccharomyces cerevisiae var. bayanus. This yeast prefermented the largest amount of sugars and thus developed lower concentration of volatile acids than Saccharomyces cerevisiae var. uvarum. However, the results of this work show that the autochthonous yeast produced the lowest ratio of volatile acids, but also somewhat lower alcohol volume (14.11 %), compared to the osmophilic yeasts (S. cerevisiae var. bayanus: 14.47 %, S. cerevisiae var. uvarum: 14.20 %).

Sweet wine; High-sugar fermentation; cryotolerant yeast

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