by Cakebread Cellars winemaker, Julianne Laks
 Wine aficionados know that the character of a wine depends upon the quality of the grapes from which it’s made, its fermentation and barrel aging, and the skill of the winemaker in harmonizing its various elements. Another key factor is rarely considered: the role of yeasts, the tiny, single-celled organisms that through fermentation convert the natural sugars in grapes to alcohol.
Almost all modern wines are fermented with a “cultured” yeast, one bred to ensure a predictable, complete and successful fermentation. After the grapes are crushed, the winemaker “inoculates” the juice with a cultured yeast strain to initiate fermentation, typically selecting a strain that brings out the best in the variety being fermented.
However, there is another type of yeast—one decidedly uncultured. These natural, airborne yeasts, present in vineyards and wineries, can spontaneously instigate fermentation in grape juice, often with unpredictable results. That’s why most winemakers introduce a cultured yeast to crowd out any native varieties that may be present. Yet, native yeasts have something to offer. Properly managed, they can enhance the complexity and vineyard character of a wine.
 In native yeast fermentation, a variety of yeasts (rather than a single, cultured strain) contributes multiple aroma and flavor characteristics, adding nuance and building complexity and texture in a wine, although some may potentially contribute undesirable characteristics, such as acetic acid, that can halt fermentation. That’s why native yeast fermentation is risky and requires more careful monitoring to avoid a stuck fermentation or the development of undesirable aromas and flavors. Conversely, such fermentations may produce wines with more vivid, multifaceted aromas and flavors.
At Cakebread Cellars, we’ve spent several years experimenting with native yeast fermentations of certain vineyard lots to determine whether they might enhance the quality and singularity of our wines, especially Sauvignon Blanc and Chardonnay. This is a challenging enterprise, because the population of native yeasts in a vineyard varies by grape variety, growing region, vintage, and even within a harvest season. (The mix of yeast species is never the same on later-harvested grapes as on early-picked ones.) Getting a firm grasp on when and to what degree native yeast fermentation may be desirable remains an ongoing process, but one we consider very worthwhile given the potential benefit of more complex and enjoyable wines.
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