Yeasts Gone Wild: Part 3.

October 17th, 2008

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

Yeast gone wild.

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

Complexity and Terroir.

The major contention of the proponents of uninoculated fermentation is that this route bestows a greater complexity to the wine. Some have suggested that certain, “regional” strains or cultures can also impart a regional distinction. S. Cerevisiae is subject to great variation (vineyard to vineyard and even tank to tank). Mortimer’s work indicated that there were multiple distinct strains within individual wineries. So it is not unreasonable to implicate yeasts as contributory factors in a wine’s distinctiveness.

But do uninoculated fermentations result in finer, more complex wines? Are inoculated wines artificial, manufactured? Larry Brooks says:

In some rare situations, like barrel fermented Chardonnay, I think the outcome can be better with non-inoculation. In most situations if you’re trying to make the most delicious wine you should inoculate.”

Morton Leslie (nom de plume of a self-reported retired Napa winemaker) is one of those who agree with the inoculation school of thought:

“The reality is that a domesticated wine yeast ends up dominating the fermentation and is responsible for the must becoming wine. If that is going to happen, why not pick the domesticated yeast you use, rather than have it determined by chance? And why not build up a healthy inoculation of that yeast so that the fermentation is clean and the character of the grape and the terroir is clearly expressed?”

So, if spoilage yeasts tend to be consistent within each vineyard and if, more often than not, S. cerevisiae ultimately dominates the fermentation process (as long as the characteristics of the other yeasts don’t dominate in a wine to the point of making it unpalatable) one could say that these wildly occurring microbes actually contribute to regional distinction.

But when you’re a hammer, it’s easy to to see a world full of nails. Which may be why people like Lisa van de Water say that the biggest problem with uninoculated fermentations are lack of predictability, spoilage aromas and stuck fermentations and consequently advocate inoculation.

Certainly, when your livelihood hinges on the finished wine’s appeal to the general public many would be reluctant to take a gamble and inoculate with cultured yeasts. Many still do, though, precisely because they feel these multi-organism, uninoculated fermentations may give in greater complexity of the resulting wine.

Josh Hermsmeyer is becoming one of those winemakers and he contests some of the assertions of the pro-inoculation school:

“I would argue that there is an upside to native ferments over and above that afforded by their cultivated brethren: terroir expression. The downsides are minimal. Natural ferments rarely stick and depending on the winemaker you ask, one man’s sulfide stink is another man’s treasure!

I had my eyes opened by a bit of research conducted by Constellation at vineyards under contract for their Ravenswood brand. Talking about the research with Joel Peterson convinced me that native ferments are that most elusive of beasts: a component of terroir that a winemaker can actually hang his hat on. In other words, there is a firm scientific basis for believing that the variation in yeast populations in native ferments each season can add identifiable sensory characteristics to wine that can be traced back to the vagaries of that particular vintage.

But native ferments have even more to offer, namely complexity. The added complexity you get from 4 different yeasts shamelessly sharing a ferment trumps the routine consistency of a monogamous relationship with just one yeast strain, no matter how pure and virtuous.”

The part where I scratch my head in search of a thundering conclusion.

If anything, this piece brought to light (for me, at least) more gray areas than clear demarcations of black and white. Some arguments made by those I contacted can compel one to chant: “Inoculate, baby, inoculate!”. Others point to the benefits to uninoculated fermentations.

It is not clear if the reported greater complexity seen in uninoculated fermentations comes from the work of several strains of S. cerevisiae working in bucket brigade fashion, or if it results from spoilage organisms like Brettanomyces, Dekkera or Kloeckera starting the ferment and then being overtaken by S. cerevisiae. Most likely, there is a bit of each scenario happening in unique proportions for each wine made in this way.

There is an undeniable gamble to this approach, but its rewards have great allure. As with all gambles, when things go wrong, they go very bad and it’s hard to “undo” the consequences.

Because the stakes in these gambles are high and any vineyard which has been operating for many years probably has a robust, established spectrum of spoilage yeasts, it is unfair to charge the people making wines (from those grapes, employing cultured yeasts) with unnatural manipulation. Complexity at the the price of a high rate of failure is a very bad business model.

Better expressions of terroir and varietal typicity with “ambient” yeasts are hotly contested issue. I have to agree with Jerry D. Murray: yeasts don’t care what variety they are fermenting. The must is their fodder, the alcohol, carbon dioxide and other products are their waste. Some organisms create waste/byproducts which are more palatable than others and they do it independently of the variety of grape or their origins.

Insofar that certain sites have unique populations of spoilage and cellar yeasts, and those can bring a unique aroma and flavor profile, then yeasts are a signature part of terroir. But it’s a sticky wicket when one delves into the question of the origins of those yeasts believed to be wild.

The biggest gray area in this discussion, in fact, is defining what really are “wild” yeasts. Are the ambient yeasts at Twisted Oak truly “wild”? Are they from previous vintages? (they’ve been making wine for a while at Twisted Oak). Are they yeasts form a bygone era, kept safe in insect’s nests and hives? Or are they truly wild yeasts which managed to survive in those same insects’ nests? Can something introduced into the winemaking process by human intervention be considered part of terroir?

I think an investigation of yeast strains in places like Calaveras County or the vineyards sourced by Ravenswood would shed a lot of light on the understanding of “wild”, “domesticated” and “feral” yeast strains. It may be worthwhile to explore the vineyard-free wilderness where insect nests could be harboring S. cerevisiae. Perhaps looking at insect nests and hives would elucidate the matter – if it has not been done already.

There is a glaring preponderance of evidence that “wild” yeasts tend to be, more often than not, spoilage species. While S. cerevisiae may enter the mix at some point (more likely at harvest time) and come to dominate the fermentation, there is nothing supporting the notion that this species has a strong enough foothold in the wild or in the vineyard to wartrant trusting every vintage to uninoculated fermenation. Still, as Larry Brooks pointed out, competent winemaking may consistently produce good, complex wines with uninoculated ferments.

 

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3 Responses to “Yeasts Gone Wild: Part 3.”

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

    [...] over at Wine Sooth has posted an exhaustive three part series on wild wine yeasts dubbed “Yeasts Gone Wild.” He even has a scandalous pic of a [...]

  2. rama Says:

    great series, thanks. surely there are winemakers out there that use commercial yeast strains and purposely stress them (underpitch, low/high ferment temperatures, no added nutrients, etc) in order to gain some of that supposed complexity you would get from a ‘wild’ ferment. that seems to me like the best of both worlds. predictable yet complex.

  3. MC Says:

    the ‘big deal’ as I see it, is not what happens during fermentaiton, it’s what happens before you inoculate. do you allow other ‘wild’ microorganisms to add to wine charachter. it’s a risky buisness and it’s far easier to kill those organisms with sulphur than to gamble. that’s why even some biodynamic growers are afraid to allow wild yeasts to lead fermentation.

    when you use comercial yeasts, you’re also gonna add enzymes and yeast food etc.. the question is how much of such wine is made in vineyard and why to grow grapes anyway?

    if you’re using pesticides, insecticides, fungicides, sintetic fertilizers and other such stuff, you surelly don’t want your must to start traditionally :)


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