Breweries, Wine, and Cheese Lifestyle

The Grapevine: Uncorking the Microbial Magic

By Elspeth Brown

I was at a wine dinner recently in which a beautiful Italian white wine was paired with a potato, caper and olive salad. I explained that the wine was natural with no added yeast. A guest asked how the wine was made if the winemaker had not added any. It was a great question because every wine must have yeast to ferment, but yeast does not necessarily have to be added. It can be naturally occurring on the grapes off the vine. Yeast shapes the wine that we drink. Without yeast, we would not have wine, but the type of yeast can ultimately alter the juice.

The purpose of yeast in winemaking is to convert the sugar in grapes to alcohol and carbon dioxide during the fermentation process. Natural, wild or spontaneous fermentation is when grape juice begins to ferment due to natural yeasts on the grape skins, and yeast in the close vicinity. Cultured yeast is commercial yeast. Commercial yeast is grown in a lab and produces reliable, fast-acting fermentation. There are different strands of yeast that can affect the flavors in wine. For instance, K1 yeast strain can help produce grapefruit flavors, while EP2 can give the wine slight floral notes. Champagne yeast is the most aggressive yeast because it converts sugar to alcohol very quickly. When a winemaker purchases these yeast strains, they know what the wine will taste like, whereas if a winemaker uses the spontaneous yeast in the vineyard, it is always a gamble.

There are pluses and minuses to using both wild yeast and cultured yeast. Wild yeast can create complexity. The fermented juice can take on different flavors and textures than typical of the varietal. Unfortunately, it has a longer fermentation which can encourage spoilage, so the winemaker must closely monitor the wine during the process. The grapes must start very healthy as well, to have success with natural yeast. If the yeast struggles during the fermentation, whether using wild or cultured, the wine will create off-putting flavors. This seems to be much more of an issue when using wild yeast. Keep in mind that when grapes are harvested, they are covered with wild yeast—some can have 50,000 yeast particles—but not all of them make good wine. Cultured yeast is reliable and consistent, and can tolerate a high level of alcohol, giving the bottled wine longevity.

The trend in the wine world over the past years is low-intervention, natural wines. I have always thought the best option is to stick with an organic or biodynamic wine that uses yeasts that are native to the area, whether spontaneous or commercial. That wine will provide a truer expression of the terroir and a consistent product that winemakers can be confident won’t be spoiled or bad. It really is magic how yeast, whether cultured or wild, can turn grapes into gold. Have fun exploring, and enjoy!

Elspeth Brown is the owner of Maggie B’s Wine & Specialty Store, 10 C South Main Street in Weaverville. For information, visit MaggieBsWine.com or call 828.645.1111.

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