http://www.nature.com/articles/srep14233
Interesting paper for the biochemically interested wine enthousiast. It shows that different populations of local wild yeasts impart different flavour profiles to wine. Quite obvious I think but now scientifically proven.
Thus, terroir can at least partially explained by differences in yeast populations.
Great link. Thank you.
The impact of indigenous and/or traditional yeasts on wine is an underestimated component of what we call terroir.
I was at Peter Lauer recently and he explained he uses the same barrels for the same wines every year (quantities allowing) for this reason in part.
I read an article in Wine & Spirits magazine that said the same kind of thing…
Interesting study. I read an article (WFW Issue 43) about research done by German wine scientist Dr. Ulrich Fischer, part of which focused on the impact on indigenous yeast. If I read his results properly, he found that there was very little consistency year to year in the microbial populations at a given site thus arguing against any consistent terroir associated with yeast . Additionally, that once alcohol levels reach ~4% in a spontaneous ferment a single strain (SC) becomes the major contributor. Experiments isolating local strains then inoculating sterile Riesling showed minimal differences in flavor profiles.
BTW, if you have access to that article in WFW, Fischer also provides a great explanation about the chemistry that produces the petrol smell in Riesling.
Chris Kissack has contributed some interesting thoughts (and scitific tidbits) on this subject. I recall te letter he wrote to WFW which he references in this blog post linked below.
http://www.thewinedoctor.com/blog/2012/08/terroir-a-matter-of-difference/
I remember hearing ~25 years ago about research in Bordeaux suggesting that the indigenous yeast contributed significantly to the characteristic flavors of the different communes.
I would imagine that the yeast has some part to play, which is why you can buy specific yeasts to provide various characteristics. Brett is often taken as terroir as well, which is one of the things Chris points out in his blog. But I’m not sure I’d accept his willingness to dismiss yeast quite so readily.
If, as most people believe, saccharomyces cerevisiae is not airborne, then it is very possible to have different plots and rows harbor different yeasts. And then there are leaf yeasts and various bacteria that may have little, if anything to do with the fermentation of sugar to alcohol but which may also contribute to flavor.
Also, as mentioned, the yeast carried in on grapes may or may not be the yeast that actually does all or any of the fermenting. In the old days people would carry a bucket of fermenting wine into a new cellar because they believed that you needed to prime the cellar. Maybe that worked, maybe not, and if it did, who knows exactly what was happening.
If anyone’s interested, here’s a study on wasps as transport vectors for fermentation yeast.
Not surprised at all. Totally makes sense.
Indigenous yeasts explain the unique sourness of sourdough bread in the San Francisco Bay Area, according to research by a USDA employee that I read about once in an airline magazine.
And I remember when Boudin’s bakery expanded to San Diego back in the last 80s, they had to fly in new starter every week or two because the mix changed over time in other locale.
All this absolutely makes sense if the winery is located in or adjacent to the vineyard, or at least in the same town, as I think at least the dominant strain of endemic yeasts has a lot more to do with the winery culture than with what’s in the vineyard. If grapes are being transported several hours (or say from the coastal mountains to Santa Rosa or San Francisco), per the sourdough, the whole idea is pretty much a crock, unless you include the producer as part of terroir. If the grapes are being transported several hours and made in a big custom crush facility where all kinds of super yeasts have been used and taken hold…
In my experience making wine, after a year in barrel the biggest difference between lots picked at the same time from the same vineyard made with native vs. cultured yeasts has to do with VA, aromatics and texture, i.e. the native yeast wines have higher VA and therefore more aromatics at the same alcohol levels, but a sharper, less textured palate. Complexity, terroir, etc etc are all very very comparable.
Many interesting thoughts!
What is missing from this paper is the dynamics of yeast growth when you inoculate with a mixture of wild yeasts. As eluded to by Kelly above, certain yeasts will dominate in the initial phase of fermentation and other substrains might take over in a later phase.
When fermenting in a facility that has been used for years, surely the yeasts will have colonized everything and all barrels must be inoculated with the same strains. Yet, I am told sometimes barrels ferment to dryness whereas others stall and have more residual sugar in the same facility. I wonder if winemakers ever genotype yeasts in these different barrels to see if different yeast strains have become predominant.
If yeasts are a main determinant of terroir, whatever that is, wineries that use commericial yeasts must not produce wines expressing terroir, no?
Regarding sourdough. I know of the existence of a sourdough starter bank in Belgium where cultures of sourdough are passaged and preserved.
Oh yeah. Regarding sourdough, you can exchange it on boards like this one. I’ve exchanged starter with people from various places. You make some, smear it on a piece of tin foil, let it dry, and mail it off. But you can start it in your own house too - just mix up some flour and water and let it sit until it bubbles. I do it every time I open a new sack of flour, just to see what I’ll get.
No idea whether the yeast comes from the air or the flour, but they are very often quite different. Some work, some not so well, some stink, some not so much. That’s why I’d probably never simply let grapes ferment on their own. Even if you did it one time and your wine was good, why wouldn’t you want to preserve that very same yeast, no matter where it came from?
How is this thread not eclipsing the Premier Cru thread? This is FAR more interesting, and compelling. The study makes great sense and is conducted well. The issue of pace of yeast activity versus cofermenting bacteria/ yeast is valid as a criticism, and aesthetic decisions about grape handling, punch down, fermentation temps all play a role of course.
As a beer brewer, it is well known and understood that different strains of yeast create completely different beers with the same source material, and that the temperature of your enzymatic hydrolysis (where you hear your barley wort and allow the polysaccharidases to cleave long starch molecules into different short- and medium-chair polysaccharides) plays a profound role in the final taste, mouthfeel, alcohol, etc.
I think yeast are an important part of place (vineyard) and time (vintage) but there is a lot of micro floura and fauna on grapes and in wineries. If wines are hit with so2 at the crusher the natives things are all but wiped out and what ever is around the winery will take over inoculated or not. If the fruit looks good I don’t add any so2 until the wines finish with ML to allow the natives to battle it out and to let tannin continue to polymerize and soften.
I have found that when specifically PN producers make wine in a central place from 5-10 vineyards the “house style” becomes more similar from wine to wine and much of the place you taste from a yeast/ml strain side is from the winery site as much as the vineyard site. Thus the reason I really only wanted to work with one vineyard on the same land where the vineyard is located in a new building that has never had any commercial strains of anything inside it. I think the ultimate sense of place and time is acheived if the winery and vineyard are together with no other micro floura or fauna incoming from other vineyards. Assuming native ferments for alcohol and ML are going to take place without the presence of so2.
Btw, this report notes regional microbial population plays a larger role than just the yeasts in the ferment.
“Microbes play key roles in the production of quality agricultural commodities for reasons ranging from their effect on crop nutrient availability via rhizosphere interactions with roots, through to their role in crop disease pressure: ultimately microbes influence plant and fruit health.”
So that, also, can effect terroir. I recall a report that showed microbial populations on the grapes skins during the maturation process had an effect on flavor/aromatic development. Of course we’re well aware of the role of a “living soil” in nutrient availability. From what we’re learning about how amazingly broad the roles of the human biome, it should be apparent that microbes play a role in how plants react to environmental cues. So, it could be a local microbe influencing budbreak or bud formation or how much energy to allocate to foliage vs fruit, and so on.
Yes, I’d guess that microbial contributions to terroir go far beyond native yeasts in the fermentation.
-Al
Joe, do winemakers preserve strains from succesful wild ferments and use them in subsequent years?
That would eliminate some risk from completely wild ferments and yet preserve some of the character.
Thanks for posting this, excellent article
I have heard of some folks that indeed do culture, store, and reproduce in house yeast. I know of some who do a small ferment(5 gal bucket or small food grade trash can) from left over grapes from berry/cluster samples each year to get an idea of what is around that vintage or more so what is not around that is a spoilage yeast or bacteria. I have also heard of folks who age longer than 12 months racking and using the lees from racking as an starter for that current harvest. You can even have the strains identified by DNA if you into that sort of thing.
I prefer to use what each year gives as I think that is a large component to the time(vintage) part of trying make wine that tastes as much of its time and place as possibile.