The objectivity of subjectivity in wine tasting and UC Davis’s first enology professor

Dr. Steve Shapin is a professor of the history of science at Harvard and a distinguished senior scholar. He’s also an oenophile. Sometimes these things mix, especially when he’s talking about the difference between subjectivity and objectivity. When they do, I end up with five or six emails from friends and colleagues saying, “Hey, Erika, did you see that wine article in [title of the most eminent academic journal in our field]?”

Yes, I did. And since you can’t, unless you belong to an institution that subscribes to Social Studies of Science, here are Dr. Shapin’s main points:

  • Maynard Amerine and the sensory science movement he engineered as the University of California Davis’s first enology professor were “objectivity engines” that turned uselessly soft subjective experience into reliably hard objective knowledge…
  • BECAUSE (at least in part) Amerine needed tools to help producers improve California’s wine quality, and then needed to be able to convince Francophilic American wine consumers that Californian wine was really, objectively, good wine
  • BUT: subjective and objective assessments are essentially dependent on each other, with the “objective” tools the product of documenting one or a group of individuals’ subjective experiences and asserting that everyone should use their terms…
  • AND: what counts as objective and subjective in any context depends on that context, and a bunch of what counts in the 20th c. Amerine/Davis tradition as Objective Wine Sensory Information would be called a subjective judgment somewhere else.

In short, capitalism (and egos or, if you’d rather, a man with a dream) had a lot to do with why we’re now all talking about raspberry and asparagus flavors instead of about elegance and finesse. Alright: some of us still use elegance and finesse, but Amerine wouldn’t have approved. Shapin, who spent time in the archive of Amerine’s papers, says that Amerine also didn’t approve of “flinty,” “petrol,” or “terroir;” the first two were characteristics he said he’d never found in wine, and the third was just the result of dirty winemaking. With very few exceptions, his terms didn’t refer to specific chemical compounds in wine (those came later, and Amerine was skeptical about explaining sensory impressions in terms of specific chemicals); they were about choosing terms that had some kind of “real” referent in sensory experience. According to his system, you could find raspberry in wine, but you couldn’t find elegance.

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Arguing “microbial terroir” from microbe to metabolite

Short: New microbial terroir research provides even more evidence that local differences in yeast and bacteria associated with a vineyard make a difference to wine quality.


Bokulich and Mills of UC Davis* have published a series of papers about the communities of yeast and bacteria that live in various winemaking-associated places and arguing for why differences in those communities – usually differences in place; sometimes differences in time – matter to wine as a finished product. Some of their past work outlines distinctive microbial communities around California and connects those communities to climate at a regional level. Their newest publication, out this week, tries to show microbial distinctiveness at the level of near-neighbor wineries and to connect those microbial profiles to wine composition.**

The article is open-access on MBio but, to be honest, it’s a challenging read if you’re interested in following the methods. The study at first seems to involve a two-way comparison between Far Niente and Nickel and Nickel, both in Oakville, California in the Napa Valley. But both of those wineries pulls grapes from multiple vineyards distributed around Napa and Sonoma, and so the comparison is actually among 13 chardonnay and 27 cabernet sauvignon wines, from different vineyard locations, fermented individually in one of those two wineries.

The first part of the study is about showing that grape musts from each of these vineyard sites have unique microbiomes (including bacteria and yeast populations), though their sample size is too small in this case to convincingly argue for a microbial basis to Napa-Sonoma distinctiveness at the AVA level. Unsurprisingly, the diversity of the microbial population and its distinctiveness decreased as fermentation progressed.

The second part of the study is about connecting initial microbial distinctiveness observed in grape musts to wine composition. The authors – and a bunch of statistics – drew some specific connections between the presence of specific metabolites (i.e. chemical compounds created during fermentation by microbial metabolism) with important sensory implications and the presence of specific microbes. On that basis, they argue (they = the authors and the statistics) that they “demonstrate that the microbial composition of grapes accurately predicts the chemical composition of wines made from these grapes and are therefore biomarkers for predicting wine metabolite composition.” That’s true in the sense that they have – in these wines, in this place – created data that mean that identifying X microbe in a must predicts finding Y chemical in a wine, for a limited number of Xs and Ys. It remains a pretty strong way of making the statement.

To be fair, the authors initial frame this as a proof of concept study. Do geographically neighboring vineyards have different microbiologies that matter to wine chemistry? Yes, in these cases, they do. More can be done to substantiate that point, and to follow up on any number of the other questions this paper raises about what some of the microbes linked to specific wine metabolites but with unknown roles in fermentation are actually doing (if they are, in fact, doing anything at all rather than serving as a marker for something else) to make that link happen.

An important note: the framing of this paper, and some others dealing with microbial terroir, can suggest the idea that terroir is quantifiable, reducible to measurable differences in straight-forward wine chemistry. That’s balderdash. Terroir is about regional character. Quantifiable chemical differences are absolutely part of that character, but so is the human history of a place, the character of the people who live there and who make the wine, and the stories that come along with it. Some of those more nebulous influences surely do translate into chemical differences, but not all of them, or at least not all of them in ways contemporary science has an easy time handling. I have no trouble believing that the stories we tell about the wine we’re drinking produce neurochemical changes that affect the sensorineural mechanics of taste perception and that effectually alter the flavor of the wine. Someday soon our sciences may be sophisticated enough to measure those changes. Someday further away, maybe our sciences will be sophisticated enough not to imagine that those measurements explain away why stories are important, too.


*Bokulich has newly moved to Northern Arizona University per the UC Davis press release, though that move is so new that he doesn’t yet seem to have a web presence at his new institutional home.

**Bokulich and Mills’ work is an interesting complement, along different lines, to the microbial terroir work Dr. Matthew Goddard’s group is doing to understand connections amongst regional populations of Saccharomyces cerevisiae, something he presented at the recent International Cool Climate Wine Symposium in Brighton and about which I’ll be writing elsewhere.

On Palate Press: Old wine research we’re still trying to finish

My piece for Palate Press this month asks what California (proto-Davis) wine researchers were doing in the era before mass spectrophotometers and DNA sequencers and even automated pH meters and all the other fancy stuff wine scientists consider essential today. The short story is that they were trying to figure out what grows best where, and how, which is fundamentally what we’re still trying to do. The long story is on Palate Press.

The long story didn’t have space for me to really geek out over the fun of reading old research articles. I think it’s fair to say that science writing — of the by scientists, for scientists variety — wasn’t as dry then as it is now, not just because antiquated language is quaint but because the distance between normal-talk and science-talk was shorter then than it is now. It’s pretty accessible and often entertaining. There’s the simple, voyeuristic pleasure of being astonished at just how backward they sometimes were, and sometimes at realizing that they weren’t as backward as we tend to assume. And then there’s the higher-order pleasure of making stories by connecting what they were doing to what we’re doing and finding new meaning in both the historical and the modern.

But reading about someone else geeking out over light archival wine reading isn’t near as fun as doing it yourself, and the archives of Hilgardia: a Journal of Agricultural Science from the University of California, including much about wine, are freely available via the University of California Agriculture and Natural Resources Respository. When so much is pay-walled and protected, free access to land grant university resources — not just for subscribers, not just for local winemakers, and not just for the taxpayers of California or even the United States — seems increasingly meaningful, and a good reminder of this massive, excellent, egalitarian knowledge-sharing project we practice through land-grant universities and agricultural extensions. I won’t ask you to excuse my unfashionable patriotism.