Structural and ultrastructural changes in yeast cells during autolysis in a model wine system and in sparkling wines

This study shows the changes that occur during the autolysis of yeast in a model wine medium and in a sparkling wine after 12 months of aging, using N omarsky Light Microscopy and Low Temperature Scanning Electron Microscopy ( LTSEM). The size of the yeasts after 24 h of autolysis in a model medium is much smaller than when they are in the growth stage. With LTSEM, a large n umber of folds can be observed on the surface of the yeast and practically empty cells. Greater morphological changes, both structural and ultrastruct ural, can be observed in the yeast after 12 months of aging in wine than in the yeast after 24 h of induced autolysis. However, less of the cytoplasmi c content of the yeast that has undergone autolysis in the wine was solubil ized than that of the yeast after 24 h of autolysis in the model wine syste m. These findings indicate that autolysis of yeast in wine is a Ion,g-lasti ng process, which continues for at least 12 months. (C) 2001 Elsevier Scien ce B.V. All rights reserved.