Characterization of the nitrogen compounds released during yeast autolysisin a model wine system

The nitrogen composition of wines aged with yeast for a long period of time , as in the case of sparkling wines, depends on the composition of the base wine and on the compounds released by the yeast. In this paper, the releas e of the different classes of nitrogen compounds during autolysis of one of the strains of yeast used in the manufacture of sparkling wines has been s tudied. The yeast, Saccharomyces bayanus, was suspended in a model wine buf fer, pH 3.0 and 10% ethanol, and incubated at 30 degrees C. Samples of the autolysate were taken after 4, 24, 48, 72, 168, and 360 h of autolysis. An electrophoretic and chromatographic study was conducted of the proteins, pe ptides with molecular weights higher and lower than 700 Da, and amino acids released during the autolysis. Using SDS-PAGE, it was observed that it was predominantly polypeptides with molecular weights lower than 10 000 that w ere released. Through HPLC of the fraction lower than 10 000 Da, it was obs erved that it is polypeptides with molecular weights of between 10 000 and 700 Da that are released first and that these later break up to give rise t o peptides with molecular weights lower than 700 Da, which in turn break do wn into amino acids. This indicates that the nature of the nitrogen compoun ds present in wines aged with yeast depends on the aging time, being less p olymerized as the aging time increases.