“There are no wild yeasts, only feral ones” Bruno D’Alfonso once told me bluntly. I had been probing the winemaker about notions in the wine loving and wine writing spheres about what is and is not excessive intervention and manipulation in modern winemaking.
Recalling my undergraduate and medical school microbiology, I had some understanding of yeasts and concepts of their utility in winemaking. Bruno’s argument made sense to me, and it affected my thinking about wine yeasts going forward.
After a recent increase in blog chatter about natural wines and the aversion some writers and critics have to cultured yeasts, I wanted to revisit this topic. Obviously, there is a disconnect between what the winemakers know and what some writers and critics believe. It seems to me, though that getting hung up over the use of inoculated yeasts as an inherently bad thing is misguided.
This is the first in a series of three posts that look at the idea of wild yeasts.
First, a little background.
What we commonly think of as yeasts, is a group of microorganisms (categorized as fungi) capable of carrying out fermentation. In this group, there are some like Brettanomyces, Dekkera and Kloeckera which can ferment wine grapes but are thought of as spoilage yeasts because they tend to produce off aromas (which result from the chemical byproducts of these yeasts’ fermentation). If those are undesirable yeasts, there is one desirable species: Saccharomyces cerevisiae. This particular yeast has had a very positive relationship with humankind for a very long time.
To get a sense of the history of this relationship, I recommend reading the shaded area (“Box 1″) in Robert K. Mortimer’s article about the evolution of the genome of Saccharomyces cerevisiae. (Dr. Mortimer is Emeritus Professor of Molecular and Cell Biology at UC Berkeley. Thanks to Larry Brooks for sharing this article with me).
Wine Myths Abound.
Lisa Van de Water, a microbiologist specializing in fermentation problems, calls it a “romantic myth” to believe that, somehow, the micro-environment of vineyard and winery select yeast strains that settle on the grapes and winery surfaces and make their way into the vineyard and, if allowed to, can result in complex wines.
Napa winemaker, Philippe Langner, echoes this, saying:
“There is always an assumption that using wild yeast produces better wines. In the imagination of some people, letting nature follow its course is best. Sometimes this works, often it doesn’t. Some wild yeast fermentations produce beautiful results but I’m sure that many more produce faulty wines and you never hear about those.“
Additionally, there is a notion of local or regionally native yeasts being somehow part of terroir or “best” for a given grape variety. Jerry. D Murray, winemaker at Oregon’s Patton Valley Vineyard, expands on this aspect of the “native yeast mythology” by saying:
“Another thing I find fascinating is the assumption that ‘native’ or ‘wild’ yeasts are somehow more ‘varietaly’ correct than cultured. That if I am making pinot noir and using cultured yeasts then I should be using a Burgundy yeast. Why, if I am not making Burgundy? And that if I grow pinot noir and employ spontaneous ferments that it somehow enhances varietal character; as if the yeast cares about what varietal [sic] is being fermented.”
It is important to remember that cultured S. cerevisiae used in winemaking is not a genetically modified organism. It is not recombinant. Nobody has “tweaked” its DNA. Cultured yeasts come from wineries, not labs. They are selections collected and grown on a nutrient-rich medium to increase their numbers. This does not result in homogeneity of organisms in the culture because a single winery is home to numerous distinct strains of S. cerevisiae.
This brings us to the idea of “natural” and “unnatural”. Many people do not understand that a human guiding hand is only a small factor. An organism’s inherent characteristics (their “nature”) are not altered when a yeast selection is made. Larry Brooks puts it this way:
“Natural does not always mean good. There’s a reason that we have selected certain tomatoes, for instance, over others and the same holds true for yeast. It is a truism that there is a range of performance for all organisms – ourselves included – if you can have organisms at the top of their range, why not? For example we do not use wild grapevines for winemaking – with good reason. And the same holds true for yeasts.
Wine is artificial in the best way – in the sense of artifice.”
The truth is out there (but is it in the vineyard?).
While numerous yeasts may grow naturally on grapes in a vineyard, Saccharomyces cerevisiae makes up a tiny minority of these microorganisms. It does not spread by airborne means like other yeasts and molds so it can’t leave the fermenter and winery surfaces and waft into the vineyard.
It has been demonstrated, that S. cerevisiae is present on surfaces in the winery and that it is carried into the vineyard from the winery by personnel, insects and on pomace used as fertilizer. However, its optimal environment is grape juice. Larry Brooks points out that the vineyard “…is not a particularly hospitable environment for them [yeasts] except during the harvest period. The grape juice itself is where they thrive.”
That S. cerevisiae is not indigenous to the vineyard has been demonstrated scientifically. In a presentation she gave in 2002 at a microbiology seminar, Van de Water said:
“…research in the past decade has shown that Saccharomyces, the yeasts used by winemakers for fermentation, are rare in the vineyard. Grape samples taken directly from the vineyard hardly ever contain any Saccharomyces yeasts at all.” (Thanks to Philippe Langner for this resource)
So the S. cerevisiae coming into the winery on fruit during harvest is not likely to be “wild” but “feral” as Bruno D’Alfonso called them. Arcadian‘s winemaker Joe Davis explains his skepticism of “wild” yeasts:
“I am always amazed at the interest in local yeast and wonder how many actually culture and identify them [the yeasts] at the time of fermentation. I often hear other winemakers talking about using only indigenous yeast and my immediate response is how do you know? Were you able to identify them and if so what were they specifically? Could it be yeast from a previous fermentation in your cellar from last week, or even last year? I have yet to have any winemaker answer that question. Too many assumptions are made that prove to be incorrect.”
Josh Hermsmeyer of Capozzi Winery, recently wrote about genetic typing of yeast species and strains at vineyards contracted by Ravenswood. Over several vintages, this identified about 30 yeast species and strains. The majority were S. cerevisiae but there were other species as well, he says.
The investigation showed that four strains of S. cerevisiae prevailed in the subsequent fermentations. I have no information, though, how these prevailing strains compared with the domesticated strains already present in the winery. Knowing that would shed more light on the origin of these yeasts.
In the next installment: “Wild-Domesticated-Feral.” and “What’s the Deal?”. Coming this Wednesday.
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