WINE YEASTS

Let's begin with the basics. Yeasts are single cell microorganisms that convert the sugar in grapes into alcohol by a process known as alcoholic fermentation (from now on referred to as AF).

Depending on the time of year, yeasts can be found in different places. In the winter, they generally live in the vineyard soil, whereas in the summer they are carried by the wind or insects, particularly bees, and cover the grape berries. As you can see, yeasts are not linked to particular grape varieties, but they do come in different strains (types of yeast). These can be either indigenous (also known as wild) or cultured yeasts and based on decisions made by the winemaker, they determine the character of the resulting wine.

[[{"fid":"8364","view_mode":"default","type":"media","link_text":null,"attributes":{"height":1840,"width":3264,"class":"media-element file-default"}}]]Agar plate with yeast colonies. The first step in cultivating yeasts.

The Saccharomyces cerevisiae paradox.

The Saccharomyces cerevisiae strain (from now on SC) is the only one capable of bringing AF to its full conclusion. Many yeast strains are present during the early stages of AF, but only our star strain can bring it to completion when conditions are right (healthy vines and temperatures not exceeding 30 degrees Celsius during fermentation).

Although SC is responsible for AF, this particular yeast strain isn't all that common in the vineyard. A paradox of nature. However, Bodegas Torres has carried out studies, which have managed to isolate indigenous yeasts that are also capable of bringing fermentation to completion.

It is worth remembering that certain yeasts do not contribute to AF. Some of these microorganisms can even cause undesirable organoleptic changes, volatile acidity or mold, and they happen to be the most abundant during the first few hours of fermentation.

Indigenous/wild yeasts vs. cultured yeasts

The discussion often revolves around the influence of yeasts and how they can produce a degree of uniformity among wines or enhance the individual nuances of a specific terroir. Which means it's not all black or white. Certain wine regions are fortunate enough to have wild strains of Saccharomyces that not only express their terroir of origin, but also display notable quality and contribute to the organoleptic characteristics of the wine. Three examples of this are the strains Montrachet, Épernay and Pasteur Champagne.

It is equally true, however, that certain cultured yeasts allow winemakers to emphasize particular wine characteristics, especially its fruitiness, because many of these strains contain aroma-enhancing esters.

Whether wild or cultured, yeasts are a crucial component in the production of great wines that display a specific personality, even though the reason for their existence is mere reproduction. The winemaking culture that has developed over the past century has established the role of yeasts in the vinification process.