Abstract
The production of volatile compounds has become one of the major technological features for yeast selection. In fact, although the aromatic profile of the wine is the sum of varietal-, pre-, post-, and fermentative-aroma compound, yeasts affect the quality of the grape from maturation throughout fermentation, metabolizing sugars and other components into alcohols, esters, organic acids, and aldehydes. Among the new technological features, the production of mannoproteins has gained interest. From this perspective, the main aim of this work was to characterize 9 strains of Saccharomyces cerevisiae and 1 of Saccharomyces bayanus for their volatile profiles and the release of mannoproteins. The strains were inoculated in Trebbiano musts and incubated at 15 °C; at the end of fermentation the wines were evaluated by GC/MS/SPME for their volatile profiles and mannoprotein content by enzymatic assay. The strains were inoculated at level ranging between 4.9 and 6.3 log CFU/mL but only the strains L318 and 12233X6167 were able to reach values of 7.5 log CFU/mL. The aromatic profiles resulted in a strain-specific fingerprinting. According to the principal component analysis, the wines produced by the strains L288, L234, and L318 were characterized by the presence of propanoic acid, butanol, octanoic acid, and 3 methyl pentanol while the wine obtained by the strain 12233x35G2 was characterized by the presence of propanoic acid, butanol, octanoic acid and 3 methyl pentanol while the strain 12233x35G2 was characterized by the presence of decanoic acid ethyl ester, heptanoic acid ethyl ester, and acetic acid 2 phenetyl ester. Regarding mannoproteins, the highest concentration was achieved by strain12233x6167 (104 mg/L). The data allowed to select the strains endowed with the best fermentation performances in terms of aroma and mannoproteins release.
Highlights
Saccharomyces cerevisiae and the other strictly related species like Saccharomyces bayanus are considered the “wine yeasts” with the highest oenological potential and are commonly used in the wine making [1]
According to the principal component analysis, the wines produced by the strains L288, L234, and L318 were characterized by the presence of propanoic acid, butanol, octanoic acid, and 3 methyl pentanol while the wine obtained by the strain
Gas chromatography combined with mass spectrometry and solid phase microextraction (SPME) represent one of the most used strategies to highlight the relation between fermentation agents and volatile molecular profile of wine [2,3,4] and represents a useful tool for the selection of new starters able to enhance sensorial properties of final products, due to the production of specifics aroma compounds [3,5,6]
Summary
Saccharomyces cerevisiae and the other strictly related species like Saccharomyces bayanus are considered the “wine yeasts” with the highest oenological potential and are commonly used in the wine making [1] They are not the numerically prevalent species on the raw material, their strong alcohol tolerance and fermentative aptitude represent a great ecological advantage allowing these species to take over quickly on the grape yeast microbiota [1]. These new criteria include yeasts ability to improve the color of wine through the formation of stable pigments; yeast β-glucosidasic activity against must-derived monoterpenes and the consequent improvement of varietal bouquet of wines [8]; production of volatile compounds able to enhance the aroma of wines such as esters, terpinols, poli-alcohols; the ability to produce and release during the alcoholic fermentation specific macromolecules able to promote wines properties like mannoproteins (MPs)
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