Cell Wall and Lipid Changes in Saccharomyces cerevisiae during Aging of Champagne Wine

Abstract

Ultrastructural changes of yeasts during aging of wine as demonstrated by thin-section electron microscopy demonstrated two principal modifications that could affect product quality. (1) Before six months, the transformation of cell walls began by the disappearance of the internal layer, even when cells were plasmolyzed. Between eight and 11 years, the mannans of external layers were in turn attacked, leaving a matrix without any affinity for silver by Thièry's reaction, which specifically visualizes polysaccharides. (2) Within six weeks after bottling, a metabolic shift led to large expanding vesicles, which were the only persisting structures inside membrane strips. This was still the case after 15 years. Analysis of yeast lipids showed that such vesicles progressively accumulated neutral lipids, while polar lipid content strongly decreased.