The power of blending: On sherry, beer, and Brexit

Friday saw me thinking a lot about blending. I awoke to the seemingly impossible news that the UK (or, more precisely, English voters, as folks here in Edinburgh will be quick to point out) had voted to leave the European Union. And then I went to work, where we’re exemplifying the power of blending multidisciplinary research teams. I sat in a synthetic biology lab populated by microbiologists, geneticists, automation and biomedical engineers, computer scientists, designers, and me (the resident social scientist), by people from across Europe, Asia, and North America, where we all ended up spending more time mutually coping with Brexit than talking about yeast genetics.

Arguments in favor of the power of blending evidently didn’t win over British separatists. I can’t help but wonder whether Remain would have prevailed if the British population spent more time with good sherry and good beer instead of gulping unthinkingly through volumes of the cheap stuff. Granted, that opinion has a lot to do with the evening’s events after I left the lab, the first of which was an informal sherry tasting.

Sherry conveys one lesson about blending: resilience comes from interdependence. Fino and Manzanilla – “biologically aged” styles – age under a blanket (the unsuspecting would probably say “scum”) of oxygen-dependent yeast. In contrast with ordinary table wines, sherry barrels are only filled partially, leaving plenty of oxygen-filled head space to let flor yeast develop on the exposed surface. That space, plus the hot climate, means plenty of evaporation, which means that barrel volumes are topped up with wine from younger barrels, and so on down the line – the solera system, which also helps build microbial consistency from year to year.

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Is hedgerow the same as sweaty passionfruit? (The social constructedness of wine at ICCWS, part II)

The International Cool Climate Wine Symposium in Brighton was an excellent chance to sample English wines, and to discover that what New Zealander’s call “sweaty-passionfruit” seems to be what English people – or at least Oz Clarke – calls the distinctively English aroma of an English countryside hedgerow.

Let it be duly noted that I’m not suggesting that Oz Clarke’s mode of description, or his palate, need be considered broadly representative of the English. Moreover, I expect that many of his countryfolk spend more time carrying laptop bags down exhaust fume-sodden city streets than carrying a rifle and a brace of dead waterfowl down “distinctively English” hedgerows. Even still. Hedgerow is a much better fit for an English wine than sweaty passionfruit, and the reverse is true for those New Zealand sauvignon blancs.

We have no absolute language for talking about wine aroma. Advocates for standardized tasting terms sometimes complain about wine writers “just calling a smell whatever” (I’m paraphrasing). Sure, everyone who writes about wine could agree to use the same words – and maybe even to take the kinds of standardized training necessary for us to all use those words in roughly similar ways – but we’d still just be calling a smell whatever. We use analogies. Wine aromas are like passionfruit, or sweat, or hedgerow, which is to say that we use memory to describe wine, which is to say that available and useful descriptions will vary amongst individuals and cultures.

Nothing new here. Plenty of folk will be familiar with efforts over the past few years to devise useful tasting terms for China and put them into use. Describing aromas of jujube or wolfberry seems more productive than trying to teach Chinese drinkers about “blackcurrant” as a wine aroma completely divorced from its associations with blackcurrants drowning in double cream or preserves spread on toast in the morning. At the ICCWS, Marianne McKay of the University of Stellenbosch described related efforts to define South Africa-relevant aroma terms. Most of her undergraduates begin knowing very little about wine, many not even being wine drinkers. Students who have to learn how to assess wine aroma at the same time as learning what to associate with “raspberry” have a harder time learning those assessment skills than students working with descriptors they already recognize. She and her colleagues are working with students to create a South African aroma wheel, which makes incredible sense. (So long as those students will work in South Africa, and one imagines that they can learn European terms later if they move to the Northern Hemisphere.)

The thing about all of these studies is that they assume that wine aromas remain identical while we just exchange one word for another. One Australian-German study actually tested the equivalency of European and Chinese wine descriptors: “dried wolfberry” was a fair replacement for “strawberry preserve,” but “fresh wolfberry” and “raspberry” didn’t match. The ideal is a one-to-one translation of the tasting note, with the sole effect increased understanding (and increased sales, those Australians are surely hoping) amongst their audience.

I disagree. Words aren’t transparent conduits for information. The words we use shape our realities. They direct where our attention travels. They activate memories and associations. We know that memory and smell are connected at the level of brain activity, and so we know that words change the way things smell.

I wonder whether “sweaty-passionfruit” as it’s used to describe sauvignon blanc and “English hedgerow” as it’s used to describe English whites both map to the same chemical compound (3-mercaptohexylacetate, or one of its cousins*), and I hope that Dr. Wendy Parr, who’s been at the center of characterizing what’s unique about the aromas of New Zealand’s signature wines, takes up that question. But even if sensory science says that these descriptors are two different words for “the same thing,” I won’t be willing to say that a mass spectrometer knows more, or better, than Oz Clarke. Not because I have any special love of Oz Clarke or mistrust in the scientific instrumentation, but because the English wine industry is in the process of shaping what’s unique about it’s terroir, and it is, and those hedgerows are part of it. Even if every English person doesn’t spend misty mornings walking down hedgerows, I’m sure that that mass spectrometer never has. 

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.

Longer:

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.