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Glutathione (GSH, γ-L-Glutamyl-L-Cysteinyl Glycine) is a tripeptide of L-glutamate, L-cysteine and glycine. GSH in wine is derived from either grapes or yeast, during alcoholic fermentation. The GSH concentration in wine is very variable and depends on the environmental conditions as well as viticultural practices. During winemaking GSH has a significant role in oxidation prevention due to its unique redox and nucleophilic properties. Since GSH is very reactive it is highly important to prepare samples immediately and under inert conditions just prior to the determination of the GSH concentration. Therefore the aim of this research was to implement a method for the quantitative determination of GSH levels in grape juices (musts) made from different Austrian grape varieties and to investigate the influence of yeast on the GSH content in wine after aging. The results of this research have shown that monitoring with nitrogen gas, sulphur dioxide and freezing process at −25 ºC led to a good protective effect on the free glutathione amount in wine and grape samples. The GSH concentration in the samples was variable. Levels were ranging from non-detectable to up to 23.10 mg/l, and it showed that grape variety has no impact on GSH concentration in the must. Furthermore the results suggest that the choice of yeast has an impact on GSH content in wine even after 6 and 18 months of aging.

In this experiment, 27 different commercial yeasts were tested for their influence on the phenols of a rose wine. The phenols depend primarily on the vine variety, cultivation and cellar processing. This experiment sought to clarify how great the influence of the yeast on the phenols is. Blaufrankisch grapes with 20° KMW were matured in the cellar with 27 different commercial yeasts. The vinification was carried out in 34 l vessels. An HPLC Agilent Technology 1220 (RRLC) with a column of ZORBAX SB-C18 15 × 2.1 mm (1.8 μm) was used for the measurement. 5 μ l of the sample were injected directly. The column oven temperature was 40 °C. The transient was 0.5% formic acid (pH = 2.3) and a gradient of methanol (3%, 4%, 14%, 30% and 70%). The detection took place at 280 and 320 nm. It was shown that the effect of yeast on phenols is low. There was a great influence on the chemical substance tyrosol. This is a phenol that can be formed by the yeast itself. The values varied between 5.4 mg and 13.2 mg/l. The already described influence of the duration of fermentation on tyrosol formation could not be confirmed.

In an experiment with Rosé wine, 27 different commercial yeasts were tested for their influence on the amino acid pattern of the wine. Amino acids are precursors for aromatic substances; therefore a large variation of the amino acid values in the wine was expected. Blaufränkisch grapes with 20° KMW were matured in the cellar with 27 different commercial yeasts. The fermentation was carried out in 34l vessels. The wines were measured for amino acids using an HP 1200 liquid chromatograph and HP-FLD1100 according to Umagat. The wines showed 13.5% alcohol and little residual sugar. The measurement results of the amino acids of the different wines showed large variations. For example, the amount of the amino acid alanine in wine varied from 17 to 138 mg. In particular, the wines of the yeast Pino Type showed the highest amounts of alanine in comparison to the other fermented wines.

The aim of the present study was to evaluate the autochthonous yeast population during spontaneous fermentations of grape musts in Austrian wine-producing areas. Investigation of genomic and genetic variations among wine yeasts was a first step towards a long-term goal of selecting strains with valuable enological properties typical for this geographical region. An approach, combining sequences of the D1/D2 domain of the 26S rRNA gene and random amplified polymorphic DNA fingerprinting, was used to characterize yeasts at the species level, whereas the differentiation of Saccharomyces strains was accomplished by amplified fragment length polymorphism fingerprinting. At the beginning of fermentation, representatives of nine genera were identified, with Hanseniaspora and Metschnikowia species characterized most frequently. Saccharomyces cerevisiae and Saccharomyces bayanus var. uvarum strains, which were identified throughout the entire fermentation process, showed a high level of genetic diversity. A number of S. cerevisiae strains were common at multiple wineries, but a wide range of strains with characteristic profiles were characterized at individual locations. This biodiversity survey represents a contribution to the investigation and preservation of genetic diversity of biotechnologically relevant yeasts in Austrian wine-making areas.

A genetic linkage map of grapevine was constructed with 92 progeny, which was derived from a cross of Welschriesling × Sirius using the pseudo-testcross strategy. Welschriesling is known for showing low magnesium uptake. The segregation pattern of this defect was compared with the segregation pattern of 251 molecular markers, 237 simple sequence repeat (SSR) and 14 random amplified polymorphic DNA (RAPD) marker. These markers were used to construct the parental genetic maps and could be arranged into 20 linkage groups. The maternal (Welschriesling) and the paternal (Sirius) maps were aligned in one consensus map. Mapmaker 3.0 software was used for the calculations of linkage groups. The genetic map rendered it possible to identify a QTL (quantitative trait loci) in linkage group 11. This loci can be associated with visual symptoms of Mg lack and the amount of Mg concentration in the leaves of the grape zone. The SSR markers VVS2 and VMC 6g1 showed the highest linkage to the core region of the Mg-QTL., José Luis Santiago is funded by a grant from Ministerio de Educacion y Ciencia of Spain.