It’s the cat tamer Chris. Today I’m going to tell you why I like indigenous yeasts… to the point where I shout about them to my friends! True story… for when we get together for a beer (because being shouted at might be one of your fantasies?).

First of all, what is yeast used for in wine?

Yeast is a single-cell fungus, a micro-organism, which enables alcoholic fermentation by transforming the grape’s sugar into alcohol. This is why the more sunshine a vintage gets, the sweeter the grape becomes (thank you photosynthesis), and higher the alcohol percentage in the wine is. Makes sense! and it’s perfectly natural.

Secondly, let’s learn the terms:

• Indigenous yeasts aka “natural yeasts” aka “wild yeasts” generally come from the grape. They can also come from the equipment and the environment in the wine cellar. We talk about yeast in the plural because you can find between 5 and 20 different strains during spontaneous fermentation. They vary throughout fermentation and from one year to another.

• Exogenous yeasts, called “chemical”, “oenological” or “added” yeasts, are all natural too (yeast cannot be created artificially, it’s grown) but they’re chosen. There is a huge amount (+250) and they are marketed based on the properties the buyer desires: revealing aromatic compounds, extracting polyphenols, controlling the fermentation temperature, flavouring (yuck), etc.

In these exogenous yeasts, there are two main categories:

• 1. Neutral, it kick starts fermentation and dominates its environment
  2. Aromatic, which we find a lot in mass-produced wines, like “grapefruit flavoured” rosés (God, help us)

You saw at the top that without yeast, there’s no fermentation, so no wine 😱.

The best is spontaneous fermentation, fermentation which starts on its own thanks to indigenous yeasts. But it’s not as simple as it seems! Because there’s life everywhere and wine yeasts are in competition with mould, other yeasts like brettanomyces (you know the ones, that stable smell), oxidative yeasts… I could go on, an entire bacteria ecosystem which can alter the wine. Making a “natural” wine is like painting a Rembrandt (see for yourself).

Are you following? So even if the indigenous yeasts have a certain authenticity, as the yeast is an integral part of the terroir (« terroir is 50% soil, climate, exposure and 50% indigenous yeasts » says Jules Chauvet), we always prioritise taste, the quality of the wine. So when there’s a risk of a deviation here – for example when it’s been a particularly rainy year which leads to some of grapes on the vine rotting – even if I’m not for it, I understand the use of neutral exogenous yeasts. They help to trigger fermentation avoiding any deviation. And so we prioritise the taste, the intrinsic quality of the wine, all while protecting an expression of the terroir.
To sum up, I really like the idea of indigenous yeasts, because they line up with my quest. And yet, it’s impossible for 99.99% of people to distinguish between indigenous yeasts and neutral exogenous yeasts in the taste of a bottle; compared to aromatic yeasts, which can be identified as they often flavour the wine in an unsubtle way.

So, the next time you go to see your wine merchant, trust them and don’t try to put them on the ropes with sulphur and indigenous yeasts. It’s more complicated than it seems… and if they’re good (we know loads, have a look), they’ll only recommend good bottles! Oh, and then be honest with yourself, would you slap Mike Tyson?

Thanks for your attention. Now, if you want to share your opinion, join us on Instagram.