Jamie Goode: Can we talk about terroir if cultured yeasts are used?

There are strong opinions about the use of cultured yeasts in winemaking. I need to acknowledge here that some years ago I did some paid work for a yeast company, Lallemand, although I haven’t done any work for them in a few years now. But the fact that I have earned money from a yeast company in the past needs disclosing. Having said this, I’m also a big fan of the natural wine movement, and most of the wines I love are made with indigenous or wild yeasts. The significance of having worked with a yeast company is that I know quite a bit about the subject of yeasts, and so I hope that my opinions here are informed.

For many people, the notion of a terroir wine is tightly coupled with the idea of using wild yeasts. The notion that local populations of yeasts present in vineyards constitute a microbial aspect to terroir is one that has gained ground now that next-generation sequencing makes it possible to see what’s actually present in the vineyard. In the past, microbes had to be cultured before you could identify them, and this selection step meant that scientists weren’t able to see everything present, just microbes that could be grown in a petri dish. Recent work has shown that in many cases wild ferments that take place in the winery are finished off by strains of Saccharomyces cerevisiae that are present in the vineyard and which are local. Interestingly, in some cases the ferments were done with yeasts that had arrived in barrels. And it’s slightly complicated story because there are also winery-resident populations of yeasts that can complete a fermentation. It used to be thought that if a winery had been using cultured yeasts in the past, then their current ferments wouldn’t really be wild, but they’d be carried out by residual yeasts from previous fermentations. This seems to be the case sometimes, but not all the time.

So if yeasts are local, surely they are part of terroir, right? This is also a complicated topic, the actual yeast populations present depending on two things. One, the weather of the year. And, two, the fungicide regime used. It seems that the fungicides used commonly in organics and biodynamics, copper and sulfur, change the microbial populations quite a bit. And because climate varies, these populations also change from year to year. For terroir effects, we really want to see something stable across years – such as the influence of the soil type. This allows us to recognize the site signature, and for terroir to be an interesting concept it has to be stable across vintages even though the wines will show vintage variation.

However, I understand why some people can’t countenance using cultured yeasts, and insist on wild ferments, even when they are making terroir wines. It’s the issue of agency.

A few years ago I visited Domaine Michel Redde in Pouilly-Fumé, in France’s Centre Loire. I stepped into the cellar with Sébastien Redde, and saw if full of large-format oak. We tasted the wines and they were soulful and distinctive. I said: ‘I assume these are all wild-ferment?’ No, says Sébastien, we use cultured yeasts. Why, I asked, a little surprised: this place had all the hallmarks of the sort of winery where indigenous ferments were the norm. His answer was that they had used wild fermentations, but found that they weren’t getting the terroir signal strongly enough. So they’d gone back to cultured yeast because they felt that gave them the clearest expression of the different sites they worked with.

For Redde this decision seems a logical one. It’s about tuning the signal to get rid of any noise. But, again, for many wineries to use a cultured yeast is something they could never consider.

Let’s remember, though, that almost all cultured yeasts were at some stage wild. They were selected from nature because they had interesting properties. Opponents of cultured yeasts claim that they are artificial and are created in the laboratory, which is not true. And with the existence of cultured non-Saccharomyces yeasts, it’s possible to emulate a wild fermentation, where several species take part in the fermentation process in a dynamic way.

Overall, we need to remember that wine is a fermented product, and that the basis of terroir is that the vines create a growth medium for the yeasts to then eat. It’s changes in this growth medium that have their origins in the vineyard site, which then influences vine physiology, that results in different compounds being produced by the yeasts as they make wine. Yeast companies love to emphasize how different yeasts can create different flavours in the wine, but a lot of this is marketing. While there are significant differences in the way yeast strains work, ultimately the yeasts are going to be affected very strongly by changes in the must (or must and skins, for red wines) and thus even the same yeast will make quite different wines given different vineyard sites.

Perhaps the best answer to the question above is: “It’s complicated”. But yes, you can absolutely talk about terroir even when using cultured yeasts. It’s all about the motivation of the winegrower. If you are setting out to make a terroir wine, you will use the toolkit of interventions you have in a wise way, and through trial and error will find a way to express your site in an intelligent way. The tools themselves aren’t the problem: it is the intention of the winegrower. It’s simplistic to suggest that a do-nothing approach will result in the truest expression of a vineyard site. As mentioned above, sometimes targeted intervention can help strip unwanted noise from the desired signal.

• Jamie Goode is a London-based wine writer, lecturer, wine judge and book author. With a PhD in plant biology, he worked as a science editor, before starting wineanorak.com, one of the world’s most popular wine websites.