The word "inoculation" can be quite the bogeyman for natural wine devotees. It comes up in reference to the introduction of cultured yeast, which has become the standard method for kick-starting fermentations in commercial wineries. This is often pitted against spontaneous fermentation, where only the grape's naturally occurring yeasts are relied on to convert sugars into alcohol. These are two schools of thought.
But what if introducing yeasts to the must could be … natural?
"Some people say I make technical wines," Louis-Benjamin Dagueneau shrugged during my recent visit to the Loire Valley. (You can read my full profile, "Three Stars of Sauvignon Blanc," in Wine Spectator's Nov. 15 issue.) He has tried letting his Pouilly-Fumé wines spontaneously ferment, but found it too unreliable—from alcoholic fermentations that last up to eight months to unwanted malolactic fermentations to wines that don't finish fermenting completely dry.
Today, he inoculates, and he's not sorry. In fact, he is skeptical when people talk about yeast diversity in spontaneous fermentation. "There's no point having seven strains if only two of them are ultimately doing the fermenting," he argues. "That's not diversity."
In a hot and dry year, for example, two strains will eat up most of the sugars. In a cold and wet year, two different strains will be the main players. "With a spontaneous fermentation, the same strains won't be assuring fermentation every year," he said.
His solution? Yeast "cocktails." He selects five native yeast strains that are found in all of his vineyards, divides his grape juice into five lots, and inoculates each in equal doses with just one strain. Once he has made sure that each strain has entirely completed fermentation on its lot, he will blend them together.
He admits it's a complicated and lengthy process, but claims it gives the resulting wines an incredible complexity. "It's an additional step in the search for the terroir's expression," he explains. "Didier [his late father] worked hard on grape varieties, to bring back diversity to the vines. As I thought it was a shame to use just one clone, I thought it was a shame to use just one yeast strain."
Dagueneau is unwavering, even as his methods have raised many an eyebrow. "Certain beliefs turn out to be completely wrong," he asserts. Conventional wisdom says that yeast strains are entirely different from terroir to terroir. "I have the same yeast population in my silex [soils] in Pouilly as in my limestone in Sancerre."
Are his yeast mixtures "human intervention"? You bet. But for him, they are key to fully expressing his terroir in the final wine—albeit in a geeky, to the point of technical, way.