Fermentation matters. Without fermentation, there would be no bread, no yoghurt, no kimchi, no beer, not even any wine. And it is yeast which makes the fermentation process happen. This microscopic single-celled fungi turns carbohydrates into alcohol and carbon dioxide, and grape juice becomes wine.

In the prehistoric dawn of winemaking, 8000 years ago, the early vintners may not have known why wine happens. They didn’t know that naturally occurring yeasts (called ambient) on the grape skin was critical – fermentation was just a miraculous, mysterious process. Relying on ambient yeast may seem a bit hit or miss, given the wide variety of yeasts that occur naturally (and can have different fermentation properties).

It’s a pretty thankless task being a yeast – as soon as the alcohol level reaches a critical strength, the yeast is killed by its own success. But not all yeasts are the same – some will tolerate a higher alcohol so are better for making strong wines out of sugar-rich grape juice. Different aroma, flavor and color characteristics in the finished wine are also influenced by the yeast used.

Millennia of experience led to an understanding that yeast matters, and that a dominant yeast strain will emerge out of the chaos in the vineyard, hopefully producing a good wine. To encourage the continuation of good yeast strains making good wine, it was traditional to return the crushed grape skins and other waste by-products of winemaking back into the vineyard to encourage good yeast.

I recently attended a talk by one of our local winemakers on how the winemaking process works, and was very interested to hear about the “superyeasts” which have been developed for precision winemaking. These aren’t the product of the dreaded “genetic modification” but rather cross-breeding of carefully selected naturally occurring yeasts from around the world. This has got to such a level of sophistication that a winemaker can order a batch of dried yeast from a catalog which will encourage very particular flavors, colors or alcoholic strength (which may have something to do with why wines today are typically several degrees stronger than they were twenty years ago).

But does this mean that carefully tailored yeasts will come to dominate winemaking in future? Maybe not. Good winemakers are careful about hygiene in their winery. Even so, yeasts will escape from the fermentation process and take up residence, waiting for their opportunity to start a new fermentation with their own characteristics. Microbiologists researching this process are coming to consider that these yeasts hanging around will in time become a dominant strain. Then old-fashioned techniques with ambient yeasts could push back against precision winemakers.

Robin Hall