Yeasts Gone Wild: Part 2.

October 15th, 2008

Yeast gone wild.  Composite from http://exploration.nasa.gov and other images available on the web.

Yeast gone wild.

This is the second post in a series of three that look at the idea of wild yeasts. (See the first post here).

Wild-Domesticated-Feral.

One of my original questions (when I set out to put this piece together) was: “are those S. cerevisiae yeasts found on the grapes prior to inoculation still “wild” or just “feral”?” If S. cerevisiae thrives primarily in close proximity of human populations (as mentioned in Robert K. Mortimer’s article – in the section discussing a theory of yeast evolution offered by Naumov), the interaction between man and yeast must have some impact on the genetic make up of the yeasts.

Philippe Langner, speculates:

It is very possible that over time cellar populations mutated to produce strains specific to a cellar. Would those wild strains be superior to the commercial ones? I don’t think many people do controlled experiments where they compare the fermentation of a wild yeast versus a good commercial yeast on grapes coming from the same block. In the end it often comes down to a philosophical point of view.

But what about areas that are just starting their wine industry? Are their indigenous S. cerevisiae yeasts truly “wild” or just “feral”? And how about areas where a wine industry goes dormant? Twisted Oak Winery‘s Jeff Stai explored this idea with me:

The yeasts up here in the hills [Calaveras County] may be the descendants of yeasts brought by 19th century settlers [Basque herders] – or the settlers may have allowed the ambient yeasts to ferment their wines – in which case they were wild and presumably continue to be. Since organized winemaking thrived in the 19th century here, and then stopped because of the end of the gold rush and prohibition – there hasn’t been a selection process going on here for quite a while.

We’re daring more and more to allow the “ambient” yeasts to ferment our wines.”

Without some testing, it can’t be said for certain if Jeff’s uninoculated fermentations are being carried out by strains from previous vintages or if the local insects are inoculating the grapes with S. cerevisiae that did not originate in his winery.

If the latter were true, these yeasts would have to be remnants from, or descendants of those strains which fermented the wines in the area’s wine industry a hundred years ago.

If we accept the model of the insect vector – which includes the insect’s nest as a place where the yeasts may remain dormant and viable – then we must consider the possibility of a pool of S. Cerevisiae outside the cellar and the vineyards. For this kind of insect vector theory to hold, there would either need to be an extended dormancy of S. cerevisiae or it would have to sustain itself at a slow growth and reproductive rate in the nests and hives.

Additionally, if that insect reservoir may hold S. Cerevisiae which originated in the winery, it may also hold S. Cerevisiae which may have been present in the environment prior to winemaking activity in the area. This would make for truly wild yeasts.

However, none of this has been demonstrated nor is it supported by scientific findings. Naumov’s postulations and supporting evidence preclude this possibility. Specifically, attempts to collect S. cerevisiae in areas removed from human populations have been unsuccessful.

What’s the Deal?

So why is the notion of “native yeasts” so popular? Why has it persisted? Why are many winemakers not willing to conduct uninoculated fermentations? Is it possible that uninoculated fermentations can be carried out cleanly and to completion?

There is no denial that the notion of uninoculated fermentation resonates with the romanticism of wine. It feeds on the notion that all things natural are better. Always candid, Morton Leslie (nom de plume of a self-reported retired Napa winemaker) offers a dose of sobering pragmatism:

“The use of indigenous yeasts versus cultured wine yeast strains is often more about PR than about wine quality. It fits a good story line both as “natural”, “non-interventionist” as well as the ever popular storyline…”we make wine like the French people do.”

It’s not that it’s impossible to make clean wines with uninoculated must. Over the centuries, some producers have had success with this approach and many still continue to make wine this way. It is, however a chancy proposition. “The simple fact is that you can either inoculate or not and still have a good outcome if you are a competent winemaker.” Larry Brooks says.

But Joe Davis remains skeptical, saying:

“To date I have yet to hear of any indigenous yeast that could carry a wine to completion in terms of primary fermentation. If so, you could bet Lalvin and Red Star would be culturing that yeast growing it on a slant and selling it to other winemakers. One has to wonder why we don’t see any Sonoma White or Napa Red in freeze dried form. You could bet I would be buying Pisoni 90210 or Fiddlestix Lollapalooza yeast if they were available.”

In the case of a first vintage in a new winery in virgin wine territory, one could conceivably have spontaneous fermentation occur with S. Cerevisiae, but the origins of that yeast are debatable. They have to come from somewhere, after all. A successful, clean and complete fermentation is not guaranteed, however, because the S. Cerevisiae would have to compete with yeast species which are naturally more abundant on wine grapes.

Larry Brooks explains that it all “depends on which strain of Saccharomyces you get and also whether other fermentative yeast species (which may grow before the Saccharomyces) caused any off flavors. There are a myriad of microorganisms in the vineyard and winery, but the only one of them adapted to surviving in the juice is Saccharomyces. So you can start with as little as a single cell and end up a few days later with Saccharomyces as the dominant organism.

My experience has been that there are vineyards that have consistent patterns of spoilage yeasts, but I think that what most researchers have found is that the population of wine yeasts in the vineyard is quite small and quite variable.”

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In the next installment: “Complexity and Terroir” and “The thundering conclusion”. Coming this Friday.

 

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2 Responses to “Yeasts Gone Wild: Part 2.”

  1. Jerry D. Murray Says:

    Arthur,

    Really great exploration of the topic. I think your quote from Larry Brooks really says it all. Good wines can be made either way. What is important is that a winemaker knows when to abort the mission and intervene with something that will get the job done. Yeast selection is really no place for unwavering committment.

  2. Bench Grafts: What I’m Up To Says:

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