Yeast: The Unsung Hero of Winemaking

Yeast is a subject that will generally turn the conversation to another topic quickly, but in the wine industry consumers and buyers are rapidly becoming more interested in what goes into producing their wine. Empson USA spoke with Manuel Marchetti of Marcarini winery to get more information.

First, it’s important to note that there is no one procedure when it comes to choosing the right type of yeast to use in the winemaking process. All strains have their pros and cons, and the trick is the find the best compromise to obtain the results a winery is looking for.

Yeast’s role in winemaking is attributed to Louis Pasteur in 1860. Before then nobody knew why fermentation happened during the winemaking process. At that time, most of the wines had high residual sugar, and many of them spoiled because of refermentation and disease.

You could say that the discovery of yeasts and the understanding of its role in transforming the glucose contained in the grapes into alcohol and carbon dioxide signaled the start of modern winemaking.

Today the wine industry separates yeast into several categories:

• Indigenous yeasts are those that you find on the skins of the grapes.
• Wild yeasts can have different interpretations but are best described as yeasts that are found outside the vineyard or are brought into the vineyard from outside (the wind, birds, insects, etc.).
• Selected yeasts belong to the species Saccharomyces Cerevisiae, and is chosen because the physiological, biochemical and ecological characteristics are optimal for the type fermentation a winery want, for example, the production of glycerol, higher or lower alcohol, less volatile acidity, etc.

The Different Uses of Yeasts

Indigenous yeast

“On the grapes, you can divide the various yeasts into groups of Saccharomyces and non-Saccharomyces. One particular thing to consider is that the Saccharomyces cerevisiae is rare on healthy grapes, but the atmosphere in the cellar can give a potential to them to develop because of contamination from the equipment, tanks, pipes, etc.

When the fermentation begins, it is tough to say which species of yeast will prevail during the fermentation and survive until the conclusion of it. The non-Saccharomyces species dominate during the first two to three days of fermentation and because of alcohol and temperature increase die and the Saccharomyces species start to prevail.

So spontaneous fermentation is characterized by a large biodiversity of inter- and intra- yeast species and this means a considerable variation during the winemaking process and the final result. This will influence the complexity of the wine and can make wines of great complexity and typicality.”

Selected Yeast

“The use of selected yeast gives you the security that you are using the Saccharomyces cerevisiae yeast, and that this species of yeast will prevail during the winemaking process. This results in a fast start of the fermentation, the complete use of the glucose contained in the grapes, shorter fermentation, less volatile acidity, less possibility of fermenting bad grapes, and gives better stability of the wine and a better fining.

The problem against of the use of them is that you can lose the wine’s natural characteristics and standardize the wine’s flavors.

Nowadays to avoid the standardization, researchers, have reproduced the yeasts that are typically present in the vineyards, like the BRL yeast found in the vineyards of Barolo.”

Manuel went on to explain that at Marcarini winery they are using different selected yeasts for each wine combines the control of select yeast without sacrificing their wines’ character. “We use selected yeasts obtained from indigenous yeasts that were discovered by researchers in the areas,” he explains “We use the BRL yeast for the Barolo Brunate and La Serra, so we do not loose typicality and at the same time we have all of the advantages of the use of selected yeast.”

By doing this Manuel has protected his winery from spontaneous fermentation, which changes the wine characteristics, and from fluctuations in the volatile acidity, caused by non-Saccharomyces yeasts, which can result in higher levels of acidity forcing you to use a larger quantity of SO2 (sulfites).

While it is not entirely possible to eliminate contact with wild yeasts, which can be involuntarily introduced during the transportation of the grapes to the winery and to the local yeasts that are present in the cellars, Marcarini’s history of quality is evidence that their passion for their craft extends beyond just the vineyard.