Yeast is a subject that will generally turn the conversation to another topic quickly, but when it comes to wine, consumers and buyers are rapidly becoming more interested in what goes into producing it. Empson recently 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 during the winemaking process. All strains have their pros and cons, and the trick is finding the best compromise to obtain the results a winery may want.
Yeast’s role in winemaking is attributed to Louis Pasteur in 1860. Before then, nobody knew why fermentation began. At that time, most of the wines had a high quantity of residual sugar, and many of them spoiled because of re-fermentation and disease.
You could say that the discovery of yeast and the understanding of its role in transforming the glucose contained in the grapes into alcohol and carbon dioxide signaled the start of modern-day winemaking.
Today, the wine industry separates yeast into a few categories:
- indigenous yeasts are those you find on the grape skins;
- wild yeasts can have different explanations, but are best described as yeasts found outside the vineyard or that are brought into the vineyard from the outside (by way of wind, birds, insects, etc.);
- selected yeasts belong to the species Saccharomyces cerevisiae, and is chosen because the physiological, biochemical and ecological characteristics are ideal for the result a winery may be looking for. For example, the production of glycerol, higher or lower alcohol, less volatile acidity, etc.
Grape Harvest
Winemaker Manuel Marchetti gave us some insight on the different uses of yeasts.
Indigenous yeast
“On the grapes, you can divide the various yeasts into groups of Saccharomyces and non-Saccharomyces. One thing to consider in particular is that Saccharomyces cerevisiae is rare on healthy grapes, but the atmosphere in the cellar can make them potentially develop through contamination from the equipment, tanks, pipes, etc.
When fermentation begins, it is tough to say which species of yeast will prevail during fermentation and which will survive until the end. Non-Saccharomyces species dominate during the first two to three days of fermentation but then because of alcohol and temperature increase, die. The Saccharomyces species then prevails.
Spontaneous fermentation is characterized by a large biodiversity of inter- and intra- yeast species, and this means there will be considerable variations during the winemaking process and final result. This influences the structure of the wine and can make wines with great complexity and typicity.”
Selected Yeast
“The use of selected yeast gives you the security of knowing you are using Saccharomyces cerevisiae yeast, and that this species will prevail during the winemaking process. This results in a quick start of fermentation, the complete use of the glucose contained in the grapes, shorter fermentation times, less volatile acidity, less chance of fermenting bad grapes, and gives wines better stability and fining.
The problem is that you can lose the wine’s natural characteristics and standardize the wine’s flavors.
Nowadays, to avoid standardizing, researchers have reproduced the yeasts that are typically present in the vineyards, like BRL yeast, which is found in Barolo vineyards.”
Manuel went on to explain that at the Marcarini Winery, they use different selected yeasts for each wine, giving them control, without sacrificing their wines’ character. “We use selected yeasts obtained from indigenous yeasts that were discovered by researchers in the area,” he explains. “We use BRL yeast for the Barolo Brunate and La Serra, so we do not lose typicity and benefit from all of the advantages of using selected yeast.”
In doing so, Manuel has protected his winery from spontaneous fermentation, which changes the wine’s characteristics, and from fluctuations in volatile acidity, caused by non-Saccharomyces yeasts, which can result in higher levels of acidity, forcing you need larger quantities of SO2 (sulfites).
While it is not entirely possible to eliminate contact with wild yeasts, which can be involuntarily introduced during the transport of the grapes to the winery, and yeasts present in the cellar, Marcarini’s history of quality is evidence that their passion for their craft extends beyond just the vineyard.
Written by Empson Staff Writer
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