NYTimes: Science Talks Terroir

Interesting article in today's NYTimes on UC/Davis folks looking at terroir:
NYTimes:SciencaAndTerroir

Tom

Is this really news? They have shown that there are differences in the flora on cuticles of grapes of different regions, and speculate that it may cause differences in perceived terroir. But one would expect differences in indigenous flora, and their hypothesis remains unproven. It remains pure speculation.

Yes, interesting and even-handed discussion of a tricky subject. I wonder why they restricted their analysis to the microbial ecology on the grapes. There is another microbial ecosystem in the soil, and it doesn't take a great leap of imagination to see how microbes in the soil, perhaps even in symbioses with the roots of the vines, could influence what ends up in the grape and consequently in the bottle. Maybe that'll be their followup publication?

Mark Lipton

Is this really news? They have shown that there are differences in the flora on cuticles of grapes of different regions, and speculate that it may cause differences in perceived terroir. But one would expect differences in indigenous flora, and their hypothesis remains unproven. It remains pure speculation.

Yup, Craig...it's news in that they have been able to identify differences in the characteristics of flora of musts from these widely scattered
areas. One would probably guess that to be the case. But connecting those differences to the sensory character in the resulting wine is, indeed, highly
speculative and associating those differences to terroir seems pretty tenuous to me.
Tom

[Robin Garr]

I just ran across this article and came here to post it. It definitely looks like important research to my humanities-major's eyes. It might tend to support what many of us have surmised, but research is generally a good way to support our impressions.

I'll paste in the first few paragraphs under an assumption of "fair use" ...

Microbes May Explain Some of the Mysteries of Terroir and Wine
By NICHOLAS WADE
The New York Times
November 25, 2013

Terroir is a concept at the heart of French winemaking, but one so mysterious that the word has no English counterpart. It denotes the holistic combination of soil, geology, climate and local grape-growing practices that make each region’s wine unique.

There must be something to terroir, given that expert wine tasters can often identify the region from which a wine comes. But American wine growers have long expressed varying degrees of skepticism about this ineffable concept, some dismissing it as unfathomable mysticism and others regarding it as a shrewd marketing ploy to protect the cachet of French wines.

Now American researchers may have penetrated the veil that hides the landscape of terroir from clear view, at least in part. They have seized on a plausible aspect of terroir that can be scientifically measured — the fungi and bacteria that grow on the surface of the grape wine.

These microbes certainly affect the health of grapes as they grow — several of them adversely — and they are also incorporated into the must, the mashed grapes that are the starting material of winemaking. Several of the natural fungi that live on grapes have yeastlike properties, and they and other microbes could affect the metabolism of the ensuing fermentation. (Indeed, several species of microbes are available commercially for inoculation along with yeast into wine fermentations.)

But are the microbial communities that grow on the grapes of a given region stable enough to contribute consistently to wine quality, and hence able to explain or contribute to its terroir?

Such a question would have been hard or impossible to address until the development of two techniques that allow the mass identification of species. One is DNA bar coding, based on the finding that most species can be identified by analyzing just a short stretch of their genome, some 250 DNA units in length. The other is the availability of machines that can analyze prodigious amounts of DNA data at reasonable cost.

Armed with these new tools for studying microbial ecology, a research team led by David A. Mills and Nicholas A. Bokulich of the University of California, Davis, has sampled grape musts from vineyards across California. Grape varieties from various wine-growing regions do indeed carry distinctive patterns of fungi and bacteria, they reported Monday in The Proceedings of the National Academy of Sciences.

Full report in The New York Times (may require subscription)
http://www.nytimes.com/2013/11/26/scien ... il0=y&_r=0

Isn’t this what “spontaneous fermentations” or so-called “wild fermentations” are all about?

Salute

Isn’t this what “spontaneous fermentations” or so-called “wild fermentations” are all about?

Salute

Not really, Victor. Studies have shown that the yeasts in those fermentations are endemic to the winery facility itself. In fact, that's true even with inoculated fermentations to a limited extent. Those darn yeasts just refuse to behave!

Mark Lipton

Tom, all it says is that different patterns are exhibited in the musts. This is a popular rather than scientific article. IT does not discuss the sensitivity of the test. Is it sensitive to one part in one thousand, in one million, in one billion? Are those microbes present dead or living, growing at a significant rate, growing at the same rate as the yeast used? Certainly, a winemaker would normally desire to inhibit all but the desired active yeast by using SO2 in active concentrations, but any growth could have been exhibited before its addition, or it could be growing, presumably very slowly, in the fermentation after the binding of SO2. If there is growth, then some of the flora would be growing at a greater rate than others, skewing the pattern. So is the pattern one in which these flora exist, or one in which these exist in a characteristic concentration relative to the others? If the latter, it would point to little activity in the must, but existence in the same relative cell densities as orignially existed on the cuticle- in other words, it was carried into the must by the skins but did not grow. Researchers have a way of wishfully thinking that their research has a universality of importance, later to discover it to have been a dead end in many cases. Without knowing more, my feeling is that this is a dead end.

Craig said:

This is a popular rather than scientific article.

The link has a link to the underlying PNAS paper.

Mark said:

Yes, interesting and even-handed discussion of a tricky subject. I wonder why they restricted their analysis to the microbial ecology on the grapes. There is another microbial ecosystem in the soil, and it doesn't take a great leap of imagination to see how microbes in the soil, perhaps even in symbioses with the roots of the vines, could influence what ends up in the grape and consequently in the bottle. Maybe that'll be their followup publication?

I made the same great leap, and was thinking that posters here could design the followup experiment. The most fun would be in the discussion of which vineyards from which regions would be best to include, and trying to get permission from those growers to harvest a tiny root sample with some dirt to get the mycorrhiza and immediately local bacterial community.

Hardest part may be finding someone who would recognize patterns in any data we generated; I know who to pay to do the sequencing... any good ideas about how to separate a representative sample of the fungi and bacteria from dirt and root scrapings?

Right, Jim, but the scientific paper is far less willing to go out on a limb about this. They seem to say that 1) there are site-specific, sometimes as well cultivar-specific flora fingerprints, 2) these flora may be found in the must at some level, 3) that they might be modified by viticultural practice, 4) that their growth in the must might be able to be modulated by enological practices (such as, but not limited to, moderating SO2), 5) that under current practices it is unknown whether their growth has any cause and effect relationship upon sensory properties. but that it could. They point to Hanseniaspora species and a couple of other wild yeasts and bacteria as having been found actually growing in must (it was isolated from a must, after all) and it and other isolates are being introduced as co-innoculae into musts, along with wine yeast. To address this, I must say that what is being introduced nowadays is first acclimated to the typical SO2 concentration and pH to be found in must, and bears little resemblace in its viability under such circumstances with the same species in the wild, unacclimated. It is well known that fastidious anaerobes such as ML bacteria, and spoilage yeasts such as Brett can grow in low-SO2 wine after the fermentation, when competition is limited, but far more difficult to imagine them competing satisfactorily under good commercial practice during fermentation. the paper uses the term "microbial terroir" as a synonym for "microbial ecosystem", not really stressing a relationship with sensorily defined terroir. While it introduces the possibility, it is tangential to the discussion and conclusions of the paper itself, and it is clear that what is getting the popular author excited is not the same thing that is getting the paper's authors excited.