About 400 of 1000 flavour compounds are yeast derived!!!
To further understand where flavours come from in wine, we need to understand that they are categorized into 3 tiers in wines: primary, secondary and tertiary.
• Primary flavours in wine are grape derived flavours – like bright green pepper in a Cabernet Franc. Although yeast play a crucial role in converting grape juice to alcohol, they also affect the development of the primary flavours. How that green pepper is perceived will be different with different fermentation dynamics. For example, are the yeast hot or cold?
• Secondary flavours are those developed during fermentation. These tend to fall into the yeasty, creamy, buttery category. Secondary aromas in wine can develop from fermentation, malolactic fermentation, and extended aging on the lees (the dead yeast).
• As wine ages, primary fruit flavours recede and more complex tertiary flavours such as nuttiness, earth, mushrooms, floral and spice may develop.
The main wine yeast is Saccharomyces Cerevisiae – this yeast is alcohol tolerate, likes warm ferments, plenty of oxygen but doesn’t like it when the alcohol gets too high. Rarely found on grapes coming in from the field, this yeast hangs around cellars.
Wild yeast – like Kloeckera and Candida – these are the yeast present on grape skins at harvest. Without an addition of sulphur dioxide these yeasts usually start fermenting, but generally die off around 5%, at which point S. Cerevisiae takes over. The wild yeast tends to produce higher volatile aromatics and are generally thought to be a little crazier to control.
A lot of wine is produced with added yeast. Specific strains are selected to bring out specific end results in wine – like increased fruitiness or smooth mouthfeel. Some yeast strains have different fermentation dynamics like low foaming or better function at low temperatures. When it comes to choosing yeast to make wine there are a lot of colours to choose from and you can dial in the stye of wine you want to make quite specifically.