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Microflora as terroir influence?



Former colleague Harvey Steiman at Wine Spectator has a nice piece on terroir in his latest blog. It actually breaks some new ground to the usual, predictably tedious conversations the wine media entertains itself with on this complicated topic. Yes, indeed, climate, elevation, the tilt of the slope or exposure to the sun”—the usual suspects—are an integral part of the mysteries of terroir, but Harvey, citing a new study out of U.C. Davis, suggests that “microflora” could be just as important.

What are “microflora”? “Bacteria and microscopic algae and fungi, especially those living in a particular site or habitat,” according to Google. The study Harvey referred to was published in the June, 2016 issue of the online medical journal, mBio, from the American Society for Microbiology.

Its main finding, which contributes importantly to the ongoing terroir discussion, albeit in “unclear” ways (a word the study itself uses), is that these microflora can account, at least in part, not only for terroir characteristics we find in “viticultural area designations” such as AVAS, but even in “individual vineyards” (and, one would expect, in individual blocks within vineyards).

The upshot? “Grape and wine microbiota exhibit regional patterns that correlate with wine chemical composition, suggesting that the grape microbiome may influence terroir.”

Scientists already had known that these microflora or microbiota exhibit identifiable…patterns across large distances,” but what surprised them seems to have been the vineyard-to-vineyard differences they found. The scientists were careful to point out that much work remains to be done before “causation” can be claimed, in the sense of why different wines of the same variety can be different when grown in close physical proximity, winemaking technique aside. But they do now believe that these neighboring microflora “demonstrate that the microbial composition of grapes accurately predicts the chemical composition of wines made from these grapes and are therefore biomarkers for predicting…terroir.”

Not all regions of wine country are “microbiologically unique,” the authors warn, and climate, soil type, topography and agricultural practices—long known to be part of terroir—also in turn may influence microflora. What, then, is the use of this study, which just seems to further muddy already muddied waters? “These markers could provide actionable information to winemakers to improve wine characteristics or mitigate problem fermentation…and could be practical for predicting the suitability of potential vineyard sites…”.

The challenges all of this poses for wine writers, which is what I’m interested in, would seem to make their tasks even more insurmountable, when it comes to writing about terroir. We at Jackson Family Wines have been doing a ton of research at understanding the various terroirs of the sub-AVAs of the Willamette Valley. It’s hard work, with source information often contradictory; the same platitudes seem to be repeated endlessly, without substantiation or proof, which, of course, only serves to prompt less diligent writers to repeat them. Getting an adequate explanation of the differences between, say, a Penner-Ash Estate and a Zena Crown Pinot Noir seems trickier than ever, now that we have microflora thrown into the equation.

The wine writer is tempted to throw up his hands in despair, but this is not allowed in analytic journalism. One must persevere, weeding out untruths from part-truths and absolute truths (which, on close inspection, often turn out to be not-so-absolute), and realizing that for every assertion, the contrary can be found; the best one can hope for is a valid consensus of all sources, rather the way things work in Biblical analysis. People—the general public—want simple, black-and-white truisms where, alas, they seldom exist. Usually, there are only shifting shapes of gray.

  1. Thanks for the shout-out, Steve. As I see it, our job as writers is not to judge “truths” but to weigh evidence—what we taste, what those involved in wine say, what scientists find—and filter them through our own experience to convey to readers.

    Sometimes science can seem “gray” because it moves so slowly. New studies can confirm or contradict what we think we knew, or the results of a previous scientific effort. Part of the magic of wine that it is so complex no one can have all the answers. Anyone who thinks they do is, undoubtedly, wrong. We’re all just trying to figure it out.

  2. Bob Henry says:

    To avoid the delay imposed by “moderation” when more than one URL is embedded in a comment, I am going to leave four discrete ones.

    “Sequencing Study Lifts Veil on Wine’s Microbial Terroir”


  3. Bob Henry says:

    Replacing the first comment’s link with a working alternate:

    “Sequencing study lifts veil on wine’s microbial terroir”

  4. Bob Henry says:

    Finding that alternate link serendipitously revealed this study:

    “Local Microbes Can Predict Wine’s Chemical Profile, Study Finds”

  5. Randy Caparoso says:

    Great stuff, Steve, Harvey and Bob… thanks! Some thoughts, out loud…

    Seems to me that much of what has always been easily observed in finished wines has never really demanded “proof” from the perspective of causation. Aromas originating from microscopic components in grapes suggesting native growth (i.e. garrigue) are commonly associated with wines from Southern France. We expect wines from Corsica or Sardinia to exhibit briny sensations. Mintiness, and sometimes cat pee, are easily idenfiable in wines grown in proximity to eucalyptus trees; and barnyardy characteristics in wines from vineyards downwind from dairy farms.

    What’s interesting is that for years non-fruit sensations have been associated more with wines from Europe as opposed to, say, California; but as more European approaches to viticulture and winemaking have been embraced in the New World, the more non-fruit sensations we find in wines from our own backyard. It doesn’t take a scientist to conclude that this is the result of increased winegrowing variables — like turning up the bass on an old Beatles record in order to hear Paul McCartney’s guitar playing front and center.

    I suspect, though, that even as researchers delve deeper into factors that have long been considered apriori in older wine regions, we’ll always have our shades of gray because, as terroir naysayers have correctly observed, human decisions impact every stage of the production process; from selections of rootstocks, spacing, trellising, etc. at planting, to yearlyl pruning, leafing, row cropping, IPM, ad infinitum. And that’s even before winemakers get into the act.

    What we can gather is that regional or vineyard-related permutations of microflora — which can be as observable as a rain event in May or bunch rot in October — certainly leaves identifiable markers on wines. Sometimes, but probably not often. The question is more, it seems, of to what extent is it even allowed? Much of our large volume commercial wine as well as smaller batch artisanal winemaking is predicated on leaving as little as possible to chance; including (or especially) pesky factors like microflora. It’s so much easier to leave that out of the equation completely; especially when the objective is to please consumers via consistency, or exert favorable response from critics or media who rate wines primarily on the basis of expectations shaped by pre-set standards.

    By the same token, no wonder there is growing interest in lower input, so-called “natural” winemaking. Many consumers (who naturally become more inquisitive once they really get into wine) simply want to know what happens when as little as possible is done to grapes. They may want wnes that meet expectations, but they also want to experience unique regional or vineyard distinctions — something Europeans began doing centuries ago.

    If microflora plays a part, it makes sense to talk it. Do journalists need substantiating “evidence” before taking on these factors in their reports? What I think they need is common sense. Plus the old adages: don’t believe everything you are told or what you read; and if you don’t know what the heck you’re talking about it, you probably shouldn’t. But in my mind, many of us have always been taling about microscopic factors anyway, even if couched more in terroir related terms. What’s the difference, except for having more rational terminology?

    Personally, I’ve always felt that a journalist’s role is to think out loud along the lines of readers’ evolving thought process. 35 years ago, when I started writing daily newspaper wine columns, it made sense to focus on things like varietal character, the exciting proliferation of premium wine producers, or the artistry of individual winemakers. These days when I write for trade, it makes sense to address their interests, like the place of wines from emerging wine regions among enduring classics. Or when I write for a “Lodi” audience, who are curious about where this region stands and how it is evolving. If we happen to come up with easier ways to talk about microflora, I don’t see why it shouldn’t be part of a discussion. Inquiring consumers and wine professionals, after all, simply want to know — and more and more of it.

  6. Yep, Bob; the literature on microbial terroir is becoming increasingly deep, and as I (granted, an erstwhile microbiologist) see it, that’s nothing but a good thing. Why the despair, Steve? Microbial terroir gives us one more set of ways to understand something that we’ve long known is incredibly complex and poorly understood. I don’t care about “fully” understanding either terroir or wine — it’s impossible, and mystery is a good thing in any case — but I do care about increasing dimensions of appreciation, and here’s one more dimension to appreciate. Good for microbiologists and for wine writers alike!

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