This week’s question via email from Ted in Sonoma, CA
I'm hearing more about "natural" wines and the wild yeasts used, can you explain what this means and its affect on the wine?
Traditional winemaking was based on native yeast fermentation, meaning no commercial yeasts were used as it commonly is today. Natural, wild yeasts are present in the air and on vegetation everywhere. When grapes are harvested and left alone, they will start fermenting on their own because of the native yeasts found on the grape skins, fermentation vessel, and in the air.
However, some winemakers prefer using commercial cultured yeasts because it allows them to control and select which strains of yeast they prefer. Every strain of yeast has a different affect on the fermentation process, and subsequently the wine. Certain yeasts perform faster and complete the fermentation in a shorter amount of time, usually within a week or two. Other yeasts work at a slower rate, which makes for a slow and steady fermentation that can take up to years to complete (this is on the extreme end). Some winemakers prefer the "get it done fast" approach so they don't have to worry about the yeasts dying or not completing fermentation. When faced with a "stuck" fermentation (a fermentation that does not finish) it is extremely difficult to get it started again. The yeast strain not only affects the rate of fermentation but also enhances certain flavors and aromas in the wine. If a winemaker wants a Pinot Noir to express more cherry, red fruit characteristics, they can select a specific strain for that.
Basically, there's a yeast strain for every style of wine and flavor/aroma character. Native fermentation, limits a winemaker from controlling anything. The winemaker's role is to sit back and let the wild yeasts do their thing. Wineries are usually unaware of which yeast strains they have floating around in their space unless they've had it tested; but even then the native yeasts in the vineyard are unknown because it varies each year. The benefit of a native fermentation is that there are usually many different strains working. Think of a painting with many different colors rather than just one---it's usually more interesting and complex. When there are many different wild yeast strains contributing to fermentation, it adds complexity and layers to the wine. Native yeast advocates believe that it allows the wine to express the terroir fully. Wines that go through native fermentation tend to have a special "funk" to them. This could be from Brettanomyces, a type of yeast that produces "off flavors" like barnyard, horse stable, band-aid, and medicinal; or from another type of yeast. Brettanomyces is generally considered a flaw and when a winemaker chooses to use native yeasts, they take the chance of Brett being one of them. If you're open to funky, interesting wines give native ferment wines a try! They will for sure stir up conversation and have you trying to identify the unfamilar aromas and flavors you sense.
These are a few of my favorite wines that are made with wild yeasts:
-The wine that made Valdiguie popular again; supple and lush with notes of sour cherry, watermelon, violets, rose, and green apple jolly rancher.
-Considered the "cult" sparkling wine of California with notes of cranberry, raspberry, blood orange, and baking spices.
-Blend of 2012 and 2011 Merlot and Cabernet Sauvignon with notes of juicy black plum, blackberry, forest floor, white pepper, and black currant.