Abstract
This study investigated the oenological potential of indigenousSaccharomyces and non-Saccharomyces yeasts isolated from different stages of the natural must fermentation process. Screening of extracellular enzymatic activities was performed on agarized media in which the following substrates were added: arbutin, cellobiose, Tween 80, tributyrin, casein and citrus pectin, to highlight the activity of enzymes: ßglucosidase, esterase, lipase, protease and pectinase. Among the 30 Saccharomyces cerevisae strains tested, 37% showed very low β-glucosidase activity, 100% showed esterase activity, 40% lipase activity, 90% protease activity and 53% pectinase activity.The non-Saccharomyces strain tested showed β-glucosidase, esteraseand protease activity. Tolerance to ethanol was assessed in YPD medium with ethanol concentrations of 5, 10 and 15% (v/v) by yeast culture development index.At 15% ethanol, development of all tested strains were inhibited. In the case of SO2 tolerance, decrease in strains development was inversely correlated with the increase in potassium metabisulphite concentration, up to 200 mg/L. Only four Saccharomyces strains showed specific oenological characteristics and were selected to be tested in mixed and/or sequential cultures to obtain wines with improved sensory features.
Highlights
The use in winemaking of the starter cultures of Saccharomyces cerevisiae had the advantage of a controlled alcoholic fermentation process, and the disadvantage of obtaining wines with deficiencies in terms of aromatic profile
The current practice of inhibiting the nonSaccharomyces yeast population which predominates at the beginning of alcoholic fermentation, by inoculation of Saccharomyces starter cultures, need to be reconsidered, due to the fact that research conducted by different authors revealed that some of these yeast strains showed superior oenological characteristics, with positive effects on the aromatic profile of wines.Soden et al (2000) showed that a positive impact on the sensory characteristics of wine is ensured by the involvement of non-Saccharomyces yeasts in the alcoholic fermentation, due to their potential to secrete extracellular enzymes
The surveys carried out in recent years allowed the selection of new strains of wine yeast both Saccharomyces, but especially nonSaccharomyces, in order to obtain and use them in mixed cultures, to improve the flavours complex of thewine and toenhance regional identity of wines.the research opened a way to increase the sensory attributes of wines, in new winemaking technologies that involvesthe management of alcoholic fermentation in similar conditions to the natural process, but initiated with both Saccharomyces and non-Saccharomycesyeasts starter cultures
Summary
The use in winemaking of the starter cultures of Saccharomyces cerevisiae had the advantage of a controlled alcoholic fermentation process, and the disadvantage of obtaining wines with deficiencies in terms of aromatic profile. The surveys carried out in recent years allowed the selection of new strains of wine yeast both Saccharomyces, but especially nonSaccharomyces, in order to obtain and use them in mixed cultures, to improve the flavours complex of thewine and toenhance regional identity of wines.the research opened a way to increase the sensory attributes of wines, in new winemaking technologies that involvesthe management of alcoholic fermentation in similar conditions to the natural process, but initiated with both Saccharomyces and non-Saccharomycesyeasts starter cultures In this context, oenological characterization of indigenous Saccharomyces and nonSaccharomyces yeasts was initiated in order to identify and select performant strains in terms of extracellular enzyme activity, which by biochemical transformations of must compounds ensure the variety and the complexity of the desired sensory characteristics of wines. By testing them in mixed and/or sequential cultures, important steps will be taken in increasing the quality and tipicity of wines
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