Abstract
Interest in the use of non-Saccharomyces yeast in mixed cultures is increasing due to the perceived improvement in the quality and complexity of the resulting wines. The aim of the study was to determine the ability of monocultures and mixed yeast cultures for deacidification and improvement of the composition of cold climate grape wines. Fermentation of grape musts with increased total acidity was carried out with the use of monocultures of Saccharomyces cerevisiae MH020215 (Sc), Zygosaccharomyces bailii 749 (Zb) and Metschnikowia pulcherrima MG970690 (Mp), and their mixed cultures, inoculated simultaneously and sequentially. Oenological parameters, organic acids and volatile compounds profiles of obtained wines were characterized. The fermentation kinetics and analytical profiles of the obtained wines showed that the use of mixed yeast cultures contributed to the reduction of volatile acidity and acetic acid content in the wines, as well as obtaining a favorable aromatic profile of the wines. The dominant higher alcohols in all wines were 2-methyl-1-propanol, 3-methyl-1-butanol and 2-methyl-1-butanol. Significantly higher amounts of the first two compounds were found in wines obtained with M. pulcherrima MG070690, both in monoculture and in mixed cultures. The monocultures of M. pulcherrima MG070690 (Mp) compared with Z. bailli 749 (Zb) synthesized higher levels of esters in wines, including ethyl acetate, ethyl propionate, isobutyl acetate, ethyl pyroracemate and isoamyl acetate.
Highlights
Organic acids present in grapes are the main source of wine acidity
The samples inoculated with S. cerevisiae MH020215 (Sc) showed clearly the best fermentation dynamics among analysed monocultures (Figure 1)
Sequential fermentation resulted in a greater reduction of total acidity in the obtained wines, as compared to the simultaneous fermentation
Summary
Organic acids present in grapes are the main source of wine acidity. The chemical composition of the grapes affects the composition of juice, and -the quality of the product. L-malic acid is accumulated mainly in the peel of the grapes and its amount is much lower in the flesh and the grape juice. This tendency may change during the ripening of the berries and due to technical treatments [3,4]. L-Malic acid contributes to the increase in wine acidity and serves as a substrate for the growth of bacteria and yeast, the presence of which leads to undesirable changes in the product after its bottling [6]. Deacidification using yeast strains has many benefits It contributes to the degradation of L-malic acid and reduces the risk of the formation of undesired compounds. The deacidification of wines with yeast offers the possibility of introducing better strategies to optimize the vinification process
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