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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.

Sparkling wines elaborated using the traditional method undergo a second fermentation in the bottle. This process involves an aging time in contact with the lees, which enriches the wine in various substances, especially proteins, mannoproteins and polysaccharides, thanks to the autolysis of the yeasts. As a result of this yeast autolysis, sparkling wines benefit from better integration of carbon dioxide and a clear sensory improvement, especially in the case of long aging. This chapter synthetizes the main results that our research group has obtained about the influence of yeasts autolysis on sparkling wines composition and quality during last years, making special emphasis on the capacity of the lees to release proteins and polysaccharides as well as on their capacity to consume oxygen and thus protect the sparkling wines from oxidation.

Climate change is affecting vine and grape physiology and consequently wine composition, causing a decrease in titratable acidity and an increase in ethanol content and pH. These effects are especially problematic in sparkling wines that need higher acidity to maintain an adequate freshness. Therefore, the wine industry is currently using certain procedures for reducing wine pH, among which cation exchange stands out as it is probably the most widely used. To study the influence of cation exchange treatment on the composition and quality of sparkling wines, a grape juice of Macabeo (pH 3.21 and titratable acidity 5.70 g of tartaric acid/L) after settling was treated to obtain a very acidic grape juice (pH 1.9 and titratable acidity 8.70 g of tartaric acid/L). The original grape juice was then blended in different proportions (0-45 %) with a treated grape juice. These different grape juices were used for obtaining their corresponding base wines which in turn were used for elaborating their corresponding sparkling wines using the traditional method. The cation exchange treatment reduced the pH from 3.15 (Control) to 2.87 (45 % of treatment) and increased the titratable acidity from 4.61 (Control) to 7.69 (45 % of treatment). No significant effects were observed on the concentration of any of the protein or polysaccharide fractions and the foaming properties of the base wine or young sparkling wines were not affected; however, cation exchange caused a decrease in foamability and persistence of the foam in older sparkling wines, especially when the proportion of treated grape juice was higher. A trained panel only found clear sensory differences in the acidity of the sparkling wines without the rest of the attributes being affected by the treatment.