The aim of the study was to evaluate the oxygen consumption kinetics of some inactivated dry yeasts in comparison with those of sulfur dioxide, ascorbic acid and glutathione.The oxygen consumption rates of three inactivated dry yeasts, sulfur dioxide, ascorbic acid and glutathione at the usual doses in a model wine solution were determined by carrying out noninvasive fluorescence measurements. The results indicate that two of the studied inactivated dry yeasts consume oxygen more effectively than sulfur dioxide.                     These data suggest that some inactivated dry yeasts may be useful for protecting wine against oxidation.This study shows for the first time that inactivated dry yeasts can actually consume oxygen, therefore opening up an interesting area for future research.

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Background and Aims: Yeast autolysis is a key step in the production of sparkling wines using the traditional method and a source of polysaccharides, mannoproteins and proteins. The evidence, however, of the enrichment of these macromolecules during ageing is not evident in the literature. In this study, autolysis of yeast lees in sparkling wines (Cava) was monitored over nine consecutive vintages. Methods and Results: The concentration of polysaccharides and proteins did not clearly increase over time, probably because these macromolecules are simultaneously released from lees and removed by other processes. In a new approach, the autolytic process was reproduced, and involved recovering the lees and maintaining them in a model wine solution for 1 year. The lees released polysaccharides and proteins, but only a small proportion of that found in the sparkling wines, especially in younger wines. Conclusions: This study confirmed that yeast enrich sparkling wines in key macromolecules but in low proportion in comparison with the usual concentration present in sparkling wine. This aspect should be considered by wineries that aim to achieve autolysis attributes, since the majority of sparkling wines are commercialised after short periods of ageing. Significance of the Study: This study determined for the first time the true contribution of yeast autolysis to the total polysaccharide and protein concentration of sparkling wines from nine consecutive vintages.

Sulfur dioxide is the most used additive today for preventing browning in grape musts and wines. However, since wine consumers are increasingly interested in healthier wines, the wine industry is keen to reduce its use. Some promising alternatives to sulfur dioxide have been proposed in recent years, including glutathione, both pure and in the form of inactivated yeasts, and Metschnikowia pulcherrima used as a bioprotective agent. Some information exists about the protective effect against oxidation of glutathione but there is very few about the use of bioprotection for that purpose. Supplementation with glutathione, regardless of the commercial form, reduced oxygen consumption and browning intensity when laccase was not present in the grape juice. Metschnikowia pulcherrima also reduced browning intensity in the absence of laccase but increased the total oxygen consumption. However, in the presence of laccase, glutathione and Metschnikowia pulcherrima were not effective enough to adequately prevent the grape juice from browning. Glutathione, both pure and in the form of inactivated yeasts, and Metschnikowia pulcherrima are interesting tools for protecting grape must against browning, and thus reducing the use of sulfur dioxide.

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