Yeasts autolysis on the manufacture of sparkling wines; Influence of aging time on the release of polysaccharides and proteins and the consumption of oxygen by the lees.

Identifier:  TDX:3202

Handle: https://hdl.handle.net/20.500.11797/TDX3202

Authors:  Pons Mercadé, Pere

Abstract:
Cava is a sparkling wine produced by the traditional method which involves two fermentations. In the first fermentation the grape juice is transformed into a base wine according to a standard winemaking process. When the second fermentation is complete, the sparkling wines are aged in the bottle in contact with yeast (also called lees) for a certain length of time, during which the process of autolysis takes place. During this ageing time, lees release macromolecules to sparkling wine matrix modulating the final composition and the quality of Sparkling wines. In addition, it is also thought, that lees enable to age longer due to their protective effect against oxidation. For this reason, winemakers say that this long contact with lees are the main difference between sparkling wines produced by the traditional method (or méthode champenoise) and those produced by other procedures. In basis of these hypothesis, a characterization of yeast autolysis in sparkling wine produced by traditional method (Cava) over long aging time inside the bottle (9 years) by: quantification of the polysaccharides and protein, following the evolution of the sensory characteristics, color and foaming properties, monitoring visual degradation of yeast over aging time using Scanning Electron Microscopy (SEM) and quantify the impact of the lees released polysaccharide and proteins in the total sparkling wine macromolecules composition. Then, an evaluation of the oxygen consumption capacity (OCR) of lees of sparkling wine elaborated by traditional method and its variation over long aging time. Furthermore, after confirming that lees really consume oxygen, a third study were set in order to confirm and understand better the mechanisms of the protective effect against oxidation by inactivated dry yeast (IDY). These OCRs were compared with the most common antioxidants used in winemaking: sulfur dioxide, ascorbic acid and glutathione to evaluate their effectiveness.