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The first thing an enologist asks is the quality of the yeast, specifically the efficiency and rapidity of fermentation that each yeast will bring to the process. One of the most important characteristics of a yeast will be its ability to quickly consume the natural grape sugars in the must.

Professor Attilio Scienza

Today's "Scienza" translation comes to us from Cynthia Chaplin in Rome. Fortuitously, Cyntha was listening to Stevie and the Professor chip at each other - in Episode 388 of the Italian Wine Podcast - while on her run. She decided to step up and help translate the professor's lesson so that the English-speaking world can appreciate his insight. Listen to Episode 388 of the Italian Wine Podcast where Stevie Kim and Professor Attilio Scienza respond to a question regarding wild and selected yeasts used in winemaking. The question was submitted by VIA Italian Wine Ambassador, Emily Wynbrandt, in New York.

About Cynthia:

Cynthia Chaplin is a professional sommelier, a member of Le Donne del Vino, and a professor of Italian wine and culture. Born in the USA, Cynthia moved to Europe in 1990 where she has lived in Spain, Belgium, France, England and Italy. She chose to center her career in Rome where she could immerse herself in the Italian wine sector, which is her passion. She teaches university students and expats, works with embassies, corporations and private clients, creating and presenting tastings, events, seminars and in-depth courses. Cynthia is a wine writer and a judge at international wine competitions, and she consults with restaurants and enotecas assisting in the development of comprehensive wine lists and excellent food pairings. She is married to her British photographer husband, Will, and they have six children ranging from 20 to 29. They live on the shore of Lake Bracciano, north of Rome, where they share their beautiful garden with one massive grapevine, two border collies and an arrogant diva cat.

Summary by Cynthia Chaplin

Question from Emily Wynbrandt:

What is the difference between selected yeasts and wild yeasts and why would an enologist choose one over the other?

Response from Professor Attilio Scienza:

The first thing an enologist asks is the quality of the yeast, specifically the efficiency and rapidity of fermentation that each yeast will bring to the process. One of the most important characteristics of a yeast will be its ability to quickly consume the natural grape sugars in the must. Second, the yeast must be able to act quickly while still preserving the favorable aromas that occur during fermentation and which create the secondary characteristics of the wine being produced. These two requirements often completely eliminate wild yeasts, which can produce unpleasant sulfurous odors and vinegar acids. Some wines, like sauvignon blanc, benefit from the thiols that form in reductive fermentation, achieving struck flint notes and fleeting delicate aromas that are valuable to the wine and give it a unique character. Wild yeasts do not allow the winemaker to sufficiently control the careful balance needed at this point in the fermentation.

The old fashioned way of creating yeasts for active fermentation involved using a technique called “pied de cuve," where unripe grapes were harvested a week or so early, turned into a must and coaxed into active fermentation, and then added to the must of freshly harvested ripe grapes, almost like an inoculation, to kickstart the fermentation.

In the 1960’s, German winemakers invented true white wine vinifcation, with the very best of modern practices. Soft pressing, centrifuges, stainless steel tanks and very low temperatures became the optimal tools for making the best white wines. These processes made it very hard for wild yeasts to do their job, as the naturally occurring yeasts on the grape skins weren’t strong enough nor numerous enough to withstand the low temperatures and the new methods eliminated the majority of the nutrients the yeasts needed to act. Selected yeasts began to gain favor where sparkling wines were being produced. These sophisticated yeasts could withstand low temperature, produced “good sulfurs” and thiols that added complexity to the wines without sacrificing the natural flavor and aromas of the grapes.

Currently, one of the bigger problems facing yeast selection is the intense cleaning protocols practiced by most modern wineries, where excessive use of detergent and hot water kills yeasts in the cantina. These practices are particularly damaging to wild yeasts. Nowadays, pinning hopes on spontaneous fermentation is very risky. The weaker wild yeasts can slow the fermentation, cause bad odors, and allow vinegar acids to develop. The main job of yeast is to intervene against the sugars. Due to the high sugar content of ripe wine grapes, which can cause mold to develop, selected yeasts need to be stronger and act faster than yeasts occurring in nature. Fermenting at low temperatures helps to prevent the wine from “burning” and losing its delicate flavors and aromas, but it makes the yeast’s job harder. We must continue to work developing selected yeasts that help preserve aromas and flavors or we run the risk of all the wines becoming homogenous and tasting the same.

Prof. Scienza’s advice to enologists is to use selected yeasts from their own territory, which express the ambience of the terroir and help the wine to speak truly of the place it comes from. This practice will assist in ensuring the unique characteristics of each individual so they continue to be representative of their region and the grapes that make them.