Winemaking yeasts

Yeast is a living micro-organism - a microscopic, single-celled fungus - used mainly for :

• fermentation of beer or wine,
• to make bread rise,
• pastry-making,
• other fermented products.

Yeast triggers the natural biochemical process of fermentation, the transformation of sugar into alcohol.

Why are wine yeasts so important? Vinification yeast play a crucial role in the production of wine. Without them, alcoholic fermentation is impossible, and therefore wine is impossible. Secondly, these yeasts give wines their personality and influence their character traits. . Fruity white wines, full-bodied reds, varietal aromas, fruity rosés - they owe much of their excellence to yeast.

For the alcoholic fermentation of grapes and the production of wine, we find mainly one species: Saccharomyces cerevisiae. This winemaking yeast is naturally present in grape must and bloom, soil and vine stocks.

The Saccharomyces cerevisiae family is valued in viticulture because :

• It presents a good resistance to ethanol,
• it resists and thrives in a wide range of conditions.

The choice of yeast used in winemaking depends on the fermentation process selected by the winemaker. In France, a distinction is made between guided fermentation (with the addition of yeast to the grape must) and spontaneous alcoholic fermentation (using only the indigenous yeasts naturally present).

Then there are the different winemaking yeasts. Each has its own properties and uses. That's why we choose yeasts adapted to white, red and rosé wines, to obtain precise, organic aromas. Some yeasts are used for rapid start-up of fermentation - known as starter yeast - while others are used for resumption of fermentation or for setting the foam.

Not all yeasts, even indigenous ones, are good for wine; some degrade the wine's characteristics and aromas.

The term "indigenous yeasts" is used to designate yeasts naturally present in grape must, soil, vines and the environment.. Indigenous yeasts trigger fermentation, but their ability to transform sugar into alcohol is limited by their sensitivity to ethanol. They are therefore used at the start of fermentation. It is also indigenous yeasts that give wines their unique signature and excellence, the expression of their terroir.

Depending on the winemaker's choice, these indigenous yeasts are often supplemented in the vat with another strain of yeast. These are known as « "selected" or "exogenous" yeasts".. They are used to accelerate fermentation, or to modify the wine's properties (texture, aromas, character, etc.). These selected yeasts are generally packaged as active dry yeast (ADY).