... at least for the yeasts. They are all trapped in the beginning, by the promises of the fresh grape juice, full of sugars and other nutrients: nitrogen, vitamins, minerals ... A true land of plenty! Drunken of joy they jump in, guzzling sugars and multiplying as if there was no tomorrow. Only to wake up with a nice hangover after some three quarters of fermentation are done. Nutrients become scarce at this stage, famine rages. Some probably try to reason, to ration, but it is already too late. Like oil, sugar is indeed a finite resource, at least in a wine vat. Then the period of dying starts. Some probably manage to escape through a pump during a final racking, but most of the natural or selected yeasts will undoubtedly end up on the bottom of the tank before the last molecule of glucose is consumed.
A boon for the winemaker because the dying mass forms the lees on which the wines will rest. When the dead yeasts decompose, they release indeed plenty of molecules that may enrich the taste and olfactory profile of the wine. The wines aged on lees thus become round and fat and gain aromatic complexity. In addition, the reducing nature of the lees (they trap oxygen) increases their resistance to air. Therefore, aging on lees, practiced primarily on white wines, can be of great benefit. At two conditions:
I. The lees have to be of good quality. This depends, among others, on the initial quality of the grapes and the course of the alcoholic fermentation. Thus, before aging on lees, we have to taste them. Otherwise, they will cause bad taste and odor.
II. The style of wine that we want to create requires fat and complexity. In other words, if the wine requires lightness and freshness, needless to fatten it like a goose.
In short: Sometimes the misfortune of yeast makes the happiness of the winemaker.
YEASTS UNDER A MICROSCOPE