Natural wines - indigenous yeasts

One point that is curiously not so known by a wide audience is the use or non-use of added yeasts for wine making. For French people there are other close examples: bread and ... cheese. Either one uses natural ferments from the milk to make cheese or one can choose to kill existing bacterias and replace them by selected ones.

These two options exist for making wines. Either keeping natural yeasts which are on the grapes after harvesting, those will do the first alcoholic fermentation. Or using SO2 and add selected yeasts. Often the later resist to sulfites and will naturally dominate or kill other yeasts.

So what is the good way of making wines? What are the respective advantages or drawbacks of both methods?

In brief fermentations are natural organic processes and the crux for winemakers is to make the good little bacterias work the best as possible. There are also bad bacterias which one wants to avoid.

Yeasts have their own taste since they create phenolic composites. (I am definitely not a specialist in organic chemistry but basically the later composites define the taste of your wines.) One talks about "neutral" yeasts or definitely less neutral ones. That is why it is sometimes funny to read some critics naming particular tastes in wine/champains while those just mainly result from a kind of selected yeasts. Better naming the yeast is not it? May be less romantic...

Killing indigenous yeast or using selected yeasts is an easy way to realize efficient and uniform wines and possibly to get a certain targeted taste. That also avoids accidents with bad bacterias. Of course one can find many scientific papers explaining that a good us of added yeasts is a very reasonable way to design wines but this idea is definitely not shared by winemakers. Anyhow one should always trust its own taste...

Now this is my personal opinion. I usually much prefer wines which alcoholic fermentation is due only to indigenous yeasts. They are much usually much more complex. Those wines can sometimes taste less "body-builded" or "perfect" but they certainly reflect more the true nature of the soil ("terroir") where the vineyard grow. I think that I can most of the time recognize added yeasts. Wines just taste efficient but simpler.

Note that there are also yeasts inherited from the cellar... That is another problem when all wines produced in a given cellar tend to have a slightly common taste...

Added yeasts is very common especially in Bordeaux. My favourite Burgundy winemakers do not use added yeasts to help the alcoholic fementation.