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11.07.2008

Semi-Debunking Wild Yeast Fermentation in Wine

If you've read many wine labels, especially those of wines that cost more than $25, you've almost certainly seen on that contains the phrase "fermented with wild yeasts" or "native yeast fermentation." This indication that the winemaker has not used a so-called "commercial" yeast is often a telltale clue as to the overall philosophy of the winemaker. Making wine without commercial yeasts can be more difficult, more unpredictable, and more risky than some are willing to accept. Those who do eschew commercial yeasts often do so because they are committed to making what they believe is a more natural wine, both for its lack of "intervention" by the winemaker, as well as because the yeasts that do end up driving the fermentation are believed to be from the vineyard and part of its ecology.

Without a doubt, making wine without commercial yeasts represents a more traditional method of making wine, but apparently the more we learn about yeasts and winemaking the less it seems that there actually is any such thing as a wild yeast fermentation.

A recent thread on the Mark Squires bulletin board addressed this very topic, and I highly encourage anyone who is interested in the subject to check it out. The discussion ranges across a number of different issues regarding yeasts, often getting quite technical, but the gist of it can be boiled down to a simple set of arguments.

First, it is clear that there are yeasts on the skins of the grapes out in the vineyards, and that when no commercial yeasts are added (and sometimes even when they are) some these yeasts can also be found working away in fermenting grapes in the winery.

However, it is also true that most of the time the yeasts that do the most work in fermenting the grapes in the winery are very different yeasts than are found in the vineyard. Which begs the question where, exactly, did they come from?

The answer, according to a lot of winemakers and researchers, is from within the winery itself. No matter how well a winery is sanitized, it tends to harbor all sorts of biological elements, including complex "cultures" of yeast that breed, mutate, and even evolve in the little ecosystem that is the winery.

If the winery ever has used commercial yeasts, this local culture will most certainly include some of these commercial yeasts. And if it hasn't it will likely include yeasts that were brought into the facility on humans, pets, equipment, insects, and more.

All of which is a long-winded way of saying that the decision to not use commercial yeasts to ferment the wine doesn't really mean that what you're getting instead is some natural cocktail of yeasts that are specific to a vineyard. A native fermentation it may be, but the yeasts that are chowing down on the grapes are much more likely to be native to the winery building than they are the vineyard, and in many cases they may include commercial yeasts as well.

I'm certainly guilty of romanticizing native yeast fermentations as a writer. Along with the decision not to fine or filter the wine, this decision generally says something to me about the quality of the wine. The fact that winemaking yeasts aren't entirely wild doesn't necessarily undermine that meaning, but it certainly does call into question just how much justification there might be for prejudice against commercial yeasts as somehow "unnatural." Biodynamic winemaking, for instance, clearly proscribes use of commercial yeasts as yet another unnatural intervention in winemaking.

The process by which grapes ferment involves sometimes 80 or more different kinds of yeasts, the actions of which are affected by pH, temperature, sugar levels, and thousands of compounds in the grapes, not to mention anything we humans might do. We're still trying to figure out just exactly how it all comes together.

As intrigued and excited as I am about the degree to which science is gradually deepening its understanding of what wine is and how it comes to be, I also love the fact that it's so complex that we've still got a long way to go.

Mystery is a good thing. It means we need to keep drinking.

Read the yeast discussion on the Mark Squires board.

Thanks to Jack at Fork & Bottle for pointing me to the discussion.

Comments (19)

Arthur wrote:
11.07.08 at 10:44 PM

I recently did a 3-part series called "Yeasts Gone Wild" that addressed this very issue.

It may be that that insect and bird nests and hives might represent a pool of S. cerevisiae in between harvests.

Hank wrote:
11.08.08 at 8:52 AM

Actually, I think the term "wild-yeast" is wrong. Its really a "ambient yeast" fermentation, which reflects the possibility of an indigenous population of yeast strains in the winery. Also, I've found that organically grown grapes do much better with ambient yeasts than those which have been sprayed with various systemic fungicides. If you use a lot of chemicals in the vineyard, you pretty much have to pitch a commercial strain to have any chance of the wine finishing dry.

Arthur wrote:
11.08.08 at 9:09 AM

"ambient" implies airborne spread. Sacc does not spread in that way. Some have called them "feral" but that carries no appeal although it is not inaccurate.

In the end the fact that we lack a good descriptor points to the fact that we don't know too much about where yeasts in uninoculated ferments come from.

Dylan wrote:
11.08.08 at 5:10 PM

Thanks for bringing this discussion back. The debate between the two philosophies has held my interest since I first heard of them--ultimately, I appreciate the greater control offered by commercial yeasts.

For the reasons I love them, I find a common bond between both wine and science: there is romance in nature, and what is natural, but, there's also a science behind all of it. As you said, science is taking things further, and yet, mystery still lingers. That's why I don't see anything wrong with using commercial yeasts which are more predictable; this work is a combination of nature and science. And in a science experiment as costly and extravagant as wine-making, it helps, to great degree, to have control over external factors. Overtime, I hope our curiosity (hypotheses/experiments) leads us to a deeper understanding of wine-making. And I hope that understanding helps us take what is inherently raw or untamed, and direct its energy toward products unlike any of us have ever tasted.

chris robinson wrote:
11.09.08 at 7:21 PM

The real issue is not between commercial or resident yeasts, but the extent to which the selected commercial yeast overwhelm the inherent aromatic and varietal quality of the grapes off a particular site, one might use the term "expression of terroir". The answer is they have a huge influence on aromatics and palate profiles making sense of place almost a joke. If we want to drink place then the arguments for locally developed yeasts are stronger. One French winemaker I know in China "flashes" the harvested must to wipe out completely any local yeast influence, probably for good commercial reason. There are machines, mainly French made, that have been designed to do this. The issue is simple - at what point does wine manipulation go beyond what one expects a vineyard to say? A $10 bottle might as well scream yeast influence. But a $50 bottle? Hmmmmm!!!

Arthur wrote:
11.09.08 at 7:49 PM

Chris,

It would appear that yeast strain-related aromatics are transient and that, after a fairly short period of time, they dissipate. I cannot recall the study or source, but I remember reading (in more than one place) that sensory assessments of wines made form the same grapes but with the use of different yeast strains showed there to be no difference in the wines after a period of time (a year maybe?).

Alder wrote:
11.09.08 at 9:28 PM

Thanks for the comments. Though I think to make such sweeping condemnations of commercial yeasts is a bit rash. There certainly are "cocktail" yeasts that are sold as providing specific aromatic qualities, but many more commercial yeasts are themselves descendants of resident yeast strains from specific areas of the world. Regardless, the idea that the yeasts themselves can strip away "terroir" is going to far in my opinion.

tom farella wrote:
11.10.08 at 9:54 AM

I agree with Aurthur that the differences from various yeasts greatly narrow with time. All too often assessments are made in the short term and dogma emerges that has lost its base. I also think that the kinetics of a fermentation are often the core difference and some of these kinetics can be managed to emulate a resident/"wild" yeast fermentation with more reliable, higher-quality results. If you've eve been burned by a wild yeast (overnight near-full ferment, stuck at 2% from killer factor, etc.), it's tough to put yourself out there again. Thank goodness that the vineyard site is the dominant source of (lasting) wine character.

Dan J wrote:
11.11.08 at 8:02 AM

I have a small private cellar where I ferment in 20-30 hl stainless steel tanks, which I steam clean when ever they have finished containing wine. I have about 7 acres of vineyard immediately surrounding the cellar. The vineyards are biologically cultivated, with only minimal copper and sulfer spraying, the last one of which occurs usually about 45 days before harvest. Our grapes are harvested in small 20kg plastic crates which are also steam cleaned and stored in the cellar during the year. The grapes are destemmed and crushed by a stainless steel destemmer-crusher which is also steam cleaned whenever it has been used. The must is pumped directly into the stainless steel tanks as described sopra with a peristaltic pump, through probably 30 meters of plastic tubing that is generally cleaned with hot water. I would estimate that the time that the must spends in contact with the destemmer-crusher pump-tube is probably around 30 seconds. The only thing I add is 3-4 mg/l of sulphites, do a quick mix-punchdown and seal the lid. I close the opening of the lid with a barrel closure. The next day I can tell that fermentation has started because when I take the barrel closure off a puff of carbon dioxide comes out of the opening. Within three-four days the ferment starts to kick in and I commence with daily pump-overs. There is a lot of energy in the ferment at about day 9-10, temps. max out at about 25 degrees C. Primary ferment ends at about day 18-20, and in most years malolactic ferment phases in smoothly during phase out of primary fermentation. I then press the wine and pump it into barrels (mix of new to 5 yr old) where it finishes malolactic fermentation sur lie at about 16-18 degrees C over the course of a month or so. I'm convinced that the wine ferments almost entirely by yeasts directly from the vineyard, any "feral" yeasts in the cellar are insignificant.

Recently I had a young enologist in the cellar who started explaining to me (what she learned at university) that fermentation yeasts in the vineyard are very few and instead yeasts in the cellar are responsible for my ferments. I suspect that the current debunking of native yeast ferment has a lot to do with biotechnological companies that need to sell their products, also intimately linked with enology schools.

I also believe that commercial yeasts significantly alter any native ferment, almost like a "filtering" operation that tends to make the wine "harmless". That's why they call it commercial yeast "innoculation".

Also, red wines are generally "raised" in barrel on lees by occasional battonage, or suspension of these lees in the wine, which give much flavor and aroma to the wine. These lees are spent yeast cells. It's obvious that commercial yeasts adds will dilute terrior character. There are also biotechnological products on the market in the form of dried-yeast cell walls, that one may add during barrel aging, which again detract from wine terrior character and add to standardized flavors.

Wine geeks out there, do not give up on native yeast ferments!

cellarette wrote:
11.12.08 at 9:05 AM

Arthur: how does wine yeast spread? In my classes at IWC, Mary Ewing-Mulligan said he preferred the term "ambient" to "wild."

Arthur wrote:
11.12.08 at 10:51 AM

Well, cellarette, it took me three very long posts to address that. The basic bullet points are: S. cerevisiae does not do well outside the juice environment, S. cerevisiae is found only areound human populations, S. cerevisiae is found on all winery surfaces where it is thought to be spread by contact vectors: hands, feet, insects (their feet) to crushers, fermenting tanks etc, S. cerevisiae is thought to be harbored in insect and bird hives/nests and is thought to be brought to the ripe grapes by these vectors around harvest time. My posts include two articles which delve into greater detail of this.

Arthur wrote:
11.12.08 at 11:42 AM

Hi again, cellarette,

I did not want to hijack the thread but Alder encouraged me to link to my posts:

Part1: http://tinyurl.com/3gesv9

Once you're there' there are links to the next installments of the series.


JR wrote:
11.14.08 at 6:31 PM

First, why do we assume that natural yeasts will somehow produce better wine. There is no reason to assume this, in fact, the yeast strains that should survive in the winery are the most adaptable, capable to mutate, able to metabolize the food source (sugar, etc. in wine) most rapidly and over the widest ranges of conditions. And it is most certainly true that these fermentations, wild or cultured, are what I call g-mish's, that is, dozens, maybe hundreds of strains finding their place in the mix over the life of the fermo. But there is no reason to believe that the strains most likely to be resident in the winery will produce the best flavor profiles. They could give two craps about flavor, they just want to convert sugar to EtOH. To me it is marketing and if I were a real winemaker instead of a home winemaker/wannabe, I would never take this risk with my wines. But alas, some do and more power to them. Oh, and Dan J., carbon dioxide is odorless. Any odor you smell in your fermentation are probably complex aromatics trapped in the headspace lifted by carbonation/tubulence/bubbles formed by the fermentation

ken Payton wrote:
11.14.08 at 9:23 PM

A comment to JR. CO2 hits you in the head like a shovel. It may be odorless but it packs a somatic wallop. Trust me.

The problem with Arthur's argument in his response to Chris above is that it is entirely textual. He refers to a 'study or source' to suggest the transience of 'wine-related aromatics' produced by one yeast strain or another. In 1997 Paul Draper said the influence of a native yeast on a wine vanished within a year. By 2003 Mr. Draper had changed his mind. A persistent influence of native yeasts was detected in horizontal tastings at Ridge. So, the distinction becomes one between the palate of one of California's most celebrated winemakers, a vigorous proponent of native yeasts, and a writer who refers to an unidentified 'study or source' as the arbiter of a wine's organoleptic qualities over time.
I'll take the winemaker's side every time. He actually tastes wine.

ken Payton wrote:
11.14.08 at 9:25 PM

I meant 'vertical' tastings.

Arthur wrote:
11.14.08 at 9:57 PM

Ken,

I think that one of the posters on the Spectator thread Alder links to cites a study or tasting. I encourage you to read that.

Ultimately, the hallmark aromas associated with specific yeasts are likely to be the fermentation esters esters so many talk about "blowing off" with time.

Arthur wrote:
11.14.08 at 10:01 PM

Correction, Wine Advocate forum thread.

In either case, this is no esoteric notion. I'll check my copy of Principles and Practices and see if there are any citations I can point you to.

Ken Payton wrote:
11.14.08 at 10:59 PM

No worries, Arthur. I'll find the relevant material.

shary wrote:
03.04.13 at 3:50 PM

Hi, I hope you can help me find a place to purchase some ambient yeast wine (wine made without any added yeast.) Please write back asap.
Thanks Shary

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