Mannoprotein Content and Volatile Molecule Profiles of Trebbiano Wines Obtained by Saccharomyces cerevisiae and Saccharomyces bayanus Strains

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.

Yeast mannoproteins: Organoleptic modulating functions, mechanisms, and product development trends in winemaking

“…However, the impacts of these genes in the production of MPs reported by researchers indicate that the modification of the culture conditions that influence the depression or overexpression of specific genes in certain yeasts could be considered to produce or release more MPs during the yeast cultivation (Gonzalez-Ramos et al, 2008;González-Ramos et al, 2010;Quirós et al, 2010). Except for the modern genetic method, traditional yeast-breeding methods including hybridization and mutagenesis were also found to be capable of breeding new types of yeasts that exhibited higher MPs production than their parental yeasts (Braschi et al, 2019;López-Malo et al, 2015;Pérez-Través et al, 2015) In recent decades, many researches have been conducted to explore the positive impacts of the non-Saccharomyces yeasts on wine quality, including their ability to improve wine aroma, stabilize wine pigments, and produce other metabolites that benefit wine quality (Casas-Godoy et al, 2021;Vejarano, 2020). Compared with the S. cerevisiae yeasts traditionally used in wine fermentation, one of the advantages many non-Saccharomyces yeasts exhibited during their growth was that they produced relatively higher amount of MPs (Table 5).…”

“…However, the impacts of these genes in the production of MPs reported by researchers indicate that the modification of the culture conditions that influence the depression or overexpression of specific genes in certain yeasts could be considered to produce or release more MPs during the yeast cultivation (Gonzalez‐Ramos et al., 2008; González‐Ramos et al., 2010; Quirós et al., 2010). Except for the modern genetic method, traditional yeast‐breeding methods including hybridization and mutagenesis were also found to be capable of breeding new types of yeasts that exhibited higher MPs production than their parental yeasts (Braschi et al., 2019; López‐Malo et al., 2015; Pérez‐Través et al., 2015)…”

“…In wine industry, the natural presence of MPs makes these compounds ideal wine organoleptic modulators. However, although the inoculation of MP-overproducing yeasts during fermentation can provide wines good quantity of MPs, the concentrations, physicochemical characteristics, and functionalities of MPs are viable and difficult to control (Belda et al, 2015(Belda et al, , 2016Benito et al, 2019;Braschi et al, 2019;Moreira et al, 2022). Therefore, the basic criteria for yeast selection during winemaking are not their ability to produce MPs, but their ability to ferment, to contribute ACs, and to stabilize wine color.…”

Role of Yeasts on the Sensory Component of Wines

“…Moreover, in addition to the ability to produce specific volatile profile fingerprinting [49], some other technological features, such as the ability to release mannoprotein, could be a criterion of selection of S. cerevisiae strains in order to increase the molecule volatile profiles. In fact, mannoproteins, constituted by mannose (85-90%) and proteins (10-15%), in addition to some positive effects on the technological properties of wines (such as improving the wine colloidal stability, reducing the tannin self-aggregation preventing the reduction of the wine acidity, reducing the protein precipitation promoting the color stabilization), can also affect the release of volatile compounds, affecting the final perception of the wine [50]. In winemaking, the addition of commercial products rich in mannoproteins can be performed, but the challenge to find mannoprotein-producing yeast can represent a great advantage also from an economical point of view.…”

Modulating Wine Pleasantness Throughout Wine-Yeast Co-Inoculation or Sequential Inoculation

“…It has been shown that the use of mannoproteins (in low amounts) or the contact of the wine with fine lees increases the levels of esters (ethyl hexanoate, methyl, and ethyl hexadecanoate, which present fruity aromas), due to the esterification of fatty acids released during yeast fermentation or yeast autolysis [121,124], while higher amounts increase, in excess, fatty acid content, producing yeasty, herbaceous, and cheese-like smells [125]. However, it has been suggested that mannoproteins can be used to remove or reduce the incidence of wine off-flavors-4-ethylguaiacol and 4-ethylphenol.…”