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What are yeasts?

31/05/2023 Winemaking

Turning grape juice into delicious wine makes us think of winemakers as people with incredible powers, but it is the yeasts that really hold the winemaking magic. These tiny things are the key to the miracle.

We want to share with you what yeasts are and how they influence the production and personality of a wine.

What are yeasts?

Yeasts are living microorganisms that are responsible for converting the sugar in the grape juice into alcohol, i.e. they transform the must into wine. This happens during the process known as fermentation.

These little allies are found naturally on the grape skins and in the vineyard environment and are what we call native yeasts.

How does the miracle happen?

Bread making also requires yeasts and, curiously, the same yeast (natural, not chemical) that is used for bread is the dominant yeast in the transformation of must into wine. It is called Saccharomyces cerevisiae and we should be very grateful to it because it also gives us beer.

During fermentation, as well as the sugar in the must being transformed into alcohol, carbon dioxide (gas) is also released, which is why yeasts also have a part to play in sparkling wines like champagne. 

At the end of fermentation, when the must has become wine, the yeasts finish their work and die, dropping to the bottom of the tank where fermentation has happened. Over time they break down releasing other compounds that can provide benefits to the wine.

What are lees?

Lees are small particles found in the wine after fermentation. They are also known as “mothers of wine”. These residues contain remains of dead yeasts, fatty acids, mannoproteins and polyphenols. Although it may seem strange, this is not just a waste product, it is actually something that brings interesting benefits. Some wines are made and aged on their lees, which gives them greater complexity for a more interesting sensory experience.

They can be used in red wines, but it is more common to find aging under lees in white wines, as they provide intensity, flavour and aromas and help to lengthen the aging potential of wines.

The way to achieve this is through battonage, which involves stirring the wine periodically with a stick to move the lees so that they can be in contact with the wine as long as possible and provide all those compounds that will benefit the wine, as we have explained.

You don’t have to use this process in winemaking; it will depend on the style and personality that the winemaker wants to bring to a particular wine.

As you can see, the work done by these little living beings is a spectacle of transformation, so every time you pour yourself a glass of wine, take a moment to thank the yeasts that, with the help of winegrowers and winemakers, are the true architects of the unique and wonderful experience in every bottle, creating the drink we love so much. Cheers to yeasts and the magic they bring to our palates!