Studying sulfur dioxide effects with better DNA technology suggests we may not need much of it

Fast: In a new study using better-than-ever microbiology, 25 mg/L SO2 added after pressing was enough to “stabilize” yeast and bacterial growth during fermentation, and higher concentrations actually seemed to slow fermentation. Inoculating the must with commercial S. cerevisiae had a very similar effect, even without adding SO2, which looks really, really good for no-added-sulfur wines. BUT (and this is a big but) the study only included one wine (a California chardonnay) made in one way, in smallish (19 L) lab volumes. Goodness only knows if their results will generalize, but let’s hope this encourages someone to look.

More: Sulfur dioxide is the single most commonly used winemaking chemical worldwide. That familiarity probably has something to do with our not understanding it better: we know it’s safe, we know how to use it, and so we don’t have much reason to study it.

In all fairness we do understand SO2 well, but microbiology keeps changing. The publishing dynamo* of Nicholas Bokulich and David Mills – responsible for really excellent recent research on how microbes are spread around a working winery over space and time – plus UC Davis wine microbiologist Linda Bisson (and another Davis student and a Japanese collaborator have published a new American Journal of Enology and Viticulture article on how SO2 affects bacteria and yeast populations in fermenting wine.

The question isn’t new, but the technology they’re using is. Short story: better DNA detection techniques let them pick up on the presence of a bigger range of both bacteria and yeast than previous strategies.

Longer story: Microbes in wine (and elsewhere, for that matter) can be “viable but nonculturable” (VBNC), a new idea ten years ago when microbiologists could still think that agar and Petri dishes were a reasonable way of identifying bugs in a sample. Until better DNA technology made clear a serious issue: yeast and bacteria might be stressed out enough by environments (like wine) to not grow on command but still be alive and able to multiply and cause problems, aka VBNC. (The unculturables who won’t grow in dishes at all are trouble, too.) The details of the high-throughput DNA sequencing they used to ensure that VBNC bugs weren’t left out of their survey aren’t important except to note that it lets them detect more microbes than previous studies.

The other great = new element of this study is its looking at multiple SO2 concentrations, from 150 mg/L down to nil. More work for them; more data for everyone. They also included ferments inoculated with commercial S. cerevisiae and not, which ended up being important.

Their results say that the most important factor in determining what grows in fermenting wine seems to be the degree to which a single strain has the opportunity to take over. One way of encouraging dominance is inoculating with commercial yeast: it more or less takes over and overall microbe diversity declines. But another way is adding SO2, which knocks down some microbes and gives tolerant ones (S. cerevisiae strains included) an opening. Adding SO2 and inoculating S. cerevisiae even without SO2 had similar effects on overall microbial diversity. And, moreover, 25 mg/L was enough SO2 to “stabilize” the ferment. In other words, sulfur-free wines may be less risky than winemakers are generally inclined to believe if they inoculate (which plenty of people inclined not to use sulfur are also inclined to avoid).

The obvious problem: one wine, one vintage, one set of processing techniques, and 19 L volumes. All of these are major reasons to question whether these results will hold for any other set of circumstances. pH and a slew of sulfur-binding compounds affect SO2 efficacy. Fermentation temperature, oxygen, clarification, means of harvesting…the list of processing steps important to microbial diversity is too long to list. And it’s well-known that fermentation volume is important to microbial kinetics.

In short? This article is almost certainly more important to wine microbiologists as a methods paper than to winemakers. (It’s not incidental that the methods section abbreviates the winemaking protocol — “grapes were harvested, crushed, and pressed according to standard winemaking procedures,” whatever that means – and uses nearly a full page of text to describe the DNA sequencing technique.) Nevertheless, it may well serve as impetus for more experimentation with low- and no-sulfur wines, and a good reminder that we always have more to learn about SO2.

Even more: find the full paper, with many more details on which specific yeast and bacteria species were detected and when they peaked (unfortunately behind the AJEV‘s lovable paywall) here. Read the full paper if you can; it contains plenty of potentially idea-generating details that I’ve not even attempted to summarize here.

*Hackneyed maybe, but, seriously, what else do you call them? Bokulich’s CV, as a PhD student, could put to shame plenty of tenured professors. When I’m not just feeling horribly inadequate, I’m wondering where this guy will end up post-graduation. Barring his speaking French and fancying living overseas – or starting a lucrative consulting firm – he’s probably lined up to make tenure at Davis in record time. Heck, he probably already qualifies for tenure.

The value of cold soaks for red winemaking; the value of cold soak research for winemakers

Cold soaking seems to be an especially divisive winemaking technique, at least in the Pacific Northwest, and that’s saying something in an industry full of strong personalities. Cold soakers say that allowing crushed red grapes to rest for one to several days in an environment too cold for Saccharomyces activity, before warming everything up to yeast-pleasing temperatures and allowing fermentation to begin in earnest, deepens color and augments flavor and tannin extraction. The anti-cold soak camp claims that these benefits aren’t real and sometimes adds that cold soaks allow for the dangerous possibility — dangerous, that is, if you’re also in the anti-spontaneous ferment camp — of illicit microbial growth before winemakers inoculate commercial yeast strains at the soak’s end.

Research to date has been unhelpfully mixed. Some studies show increased phenolic (color and/or tannin) extraction, some don’t, some even show lower phenolics following cold soak, and the variables responsible for the differences haven’t yet been worked out. Adding to the confusion is the inevitable mess that follows pro-spontaneous from anti-spontaneous fermenters, since the non-Saccharomyces activity that might occur during cold soaks is a source of desirable complexity to some and unconscionable spoilage to others.

I would love to say “until now” and herald the arrival of a brilliant, conclusive paper outlining a robust explanation for how and why and where and when cold soak works. My inability to do so isn’t likely to come as a surprise. Nevertheless, there is new research and, while far from once-and-for-all conclusive, it helps, if perhaps not in the expected way. A new study from an Argentinian team* tested cold soak on cabernet sauvignon, merlot, syrah, pinot noir, malbec, and barbera d’asti, looking for differences both when the wines were pressed and after a year of bottle aging. Cold-soaked wines saw four days of 6.5-11.5ºC (44-52ºF) courtesy of periodic dry ice additions, then 10-day fermentations at 21.5-26.5ºC (71-80ºF); control wines went straight to 14-day fermentations. All varieties were made in the same way: same full twice-daily pump-overs, same twice-daily punch downs. All were inoculated with the same commercial yeast strain five hours after crush. Regrettably, the study didn’t include multiple variations on the cold soak theme — different times, temperatures, or techniques — that might have helped to suss out where any cold soak differences are happening and given much more information to winemakers. In particular, it’s important to emphasize that chilling with dry ice meant as much as a 10ºC (18ºF) difference in temperature between different parts of the tank because the dry ice clumped. Jacketed tanks would have applied a more uniform treatment.

The agglomerated results were straightforward enough. Cold soaks increased color density, but didn’t increase phenol or tannin concentrations. Cold soaking also didn’t make a statistical difference to any basic wine chemistry parameters: ethanol concentration, pH, acids, glycerol, and residual sugar. Tasters found that the most important difference between all of the wines was driven by grape variety, though that’s hardly meaningful and says nothing about cold soak. That’s the big picture.

The details in the supplemental data attached to the main paper show something more interesting. Each variety responded a bit differently to the cold soak treatment. In the barbera and the syrah, tannin concentrations actually were higher in the cold-soaked wines. The opposite was true for the pinot noir, where cold-soaked wines measured tannin concentrations statistically significantly lower than the control. Cold soaking related to increased total phenols in cabernet, decreased in pinot noir.

What this says to me is that we’re measuring the wrong construct at the wrong level of detail. Asking whether “cold soak” works seems to be the wrong question. Instead, we need to be testing out different potential cold soaking parameters in specific grape varieties to identify what precisely makes a difference and what is moot. This is the kind of data that could really help winemakers who through the lens of their communal experience are saying that cold soak sometimes makes a noticeable positive difference and sometimes doesn’t, and who might reasonably look to science to help them figure out what features separate the worthwhile instances from the useless ones. Unfortunately, if the research question continues to be “Does cold soak increase phenol concentrations?” instead of “Under what conditions does cold soak make a difference to phenol concentrations?” we’re likely to continue seeing confused yes-no-or-maybe reports instead of useful, applicable explanations of what winemakers seem to observe.

 

*Including Federico Casassa, who has in the past published excellent phenol-related research with James Harbertson at Washington State University, including the American Society of Enology and Viticulture’s 2014 Best Enology Paper of the Year, on the phenolic effects of extended maceration and regulated deficit irrigation, the full text of which is freely available here.

Authenticating icewine: closer, if not quite close enough

Scenario #1 – You’re sitting next to your fire after dinner, relaxed, with a few ounces of fine Canadian or German icewine, maybe a few slices of blue cheese and a ripe comice pear, and the current evening reading book. You enjoy all three for an hour or so and retire, happy and sleepy, to bed.

Scenario #2 – You’re sitting next to your fire after dinner with a few ounces of icewine and an active mind in search of a target, maybe two active minds if you have a companion. Conversation turns to the wine, how desperate those first Germans must have been to salvage their inadvertently frozen grapes and how arduous and expensive repeating the process on purpose now is. You speculate that cutting real icewine with something else must be mighty tempting, and the gaze you cast on your glass turns wary. And then you cast your gaze on Google and find this new article in the American Journal of Enology and Viticulture on a new strategy for testing the authenticity of icewine.

Icewine production is very expensive and no International Body of Icewine Authenticators polices producers to ensure that they’re doing it right or in good faith. Canada produces the bulk of the world’s stock (though I also enjoyed some fine examples in the Finger Lakes, not too far south of Ontario), and the Canadian Vintner’s Quality Alliance (VQA) legislates use of the term: a Canadian bottle with “icewine” or “ice wine” on the label must be made from approved varieties, from grapes harvested during “sustained” temps of at least -8°C, naturally frozen on the vine, coming in at at least 35°Brix, with no added sugar or alcohol, all overseen by a VQA representative. European producers employ similar standards, but the Asian sweet wine market is apparently well-populated with “Iced wine” and other unauthorized and fraudulent variations on the theme. Having a reliable means to verify that an “icewine” is really icewine made from frozen grapes seems prudent.

Per Armin Hermann’s new research, tracking oxygen isotopes could be that way. The idea is clever and conceptually simple. When grapes freeze, water partitions unequally between the part that turns to ice and the part that remains liquid. That’s the point of icewine: more water freezes, leaving sugars and other dissolved molecules concentrated in the syrupy liquid that remains. The naturally occurring isotope 18O, present in the water, will also distribute into the frozen and the unfrozen parts unequally. Since the frozen ice is more or less excluded from what ends up in a bottle of true icewine, then, icewines will contain a characteristic amount of 18O. All we need to do is determine — theoretically, using mathematical equations, and empirically, by measuring a bunch of icewines — what the “icewine” versus the “not icewine” 18O ranges are. Simple, elegant, and probably effective.

The plots of 18O measurements Hermann created show what looks like reasonably convincing separation between the ice- and non-icewine samples (understanding that judging how convincing is outside my expertise). BUT, there are two important caveats. First, the comparison was lab-frozen grape musts against the unfrozen originals. Again, it’s simple: “Frozen grapes, when pressed, will produce a must that is always depleted in 18O relative to its marc and also to their unfrozen counterparts.” The study didn’t include creating a database of icewine samples from various regions to establish reasonable 18O ranges. That’s solvable in theory, though the success of the whole method still depends on finding good, clear separation between real live ice and non-icewines.

Second, the method provides no way of determining how the wine was frozen. The 18O-depleted wine could have just as easily been frozen after harvest, in the winery, illegally. So, no matter how successful that empirical database is, the method won’t perfectly solve the how-do-we-detect-fakery problem. It is, as Hermann notes, an “additional” means giving a “strong indication” of authenticity. I wonder: is there a detectable chemical difference between the kind of slow freezing that would happen naturally on a grapevine in a cold Ontario winter and fast winery cryofreezing? Until then, looking for the Canadian VQA mark on the bottle — and avoiding anything labeled “iced wine” — remains the safest option, North American privilege notwithstanding.

Wine research news: the improbable edition

Some wine research is revelatory: it provides an “aha!” moment for some long-standing grape growing or winemaking question. Some wine research is disappointing: it doesn’t come up with the answer we wanted, or an answer at all. And some wine research is just plain weird. This week, a few entries in the weird category:

Using fruit flies as model sniffers – Drosophilia melanogaster, the common fruit fly, ranks right up there with the mouse and Escherichia coli as a hyper-common lab animal: their giant chromosomes make them easy targets for genetics research. What I didn’t know before? They’re also good for sniffing research. Some computational neuroscientists in the UK used flies to look for differences between brain responses to familiar and unfamiliar odor molecules? Familiar for a fly? Wine aroma molecules, of course. No word from the research group on whether the flies’ tasting notes will be released at a later date.

Impregnating yeast with wood aromas – We have oak adjuncts: cheap, convenient chips to mimic expensive, bulky barrels. We have lees aging: letting wine sit on the sludge of dead yeast cells left over after fermentation to yield flavor and texture. Ever thought of putting the two together? The idea somehow occurred to a group of Spanish enologists, who used the sometimes-spongelike qualities of yeast cell walls to absorb flavors from wood chips, then steeped the yeast gunk in red wine. The “wood-aromatised yeast lees” released woody flavors back into the wine, and both tasters and chemical analyses could show a difference (tasters particularly appreciated chestnut-infused wine, which was more plummy and spicy than oak, acacia, or cherry wood). The idea appears to be making wood-flavored wine faster, though it’s hard to see why using dead yeast as wood chip sponges is better than just using the wood chips.

Grape marc as an herbicide – Grape marc (or pomace, or solid leftover grape bits) isn’t usually considered toxic. Quite the contrary: it’s a common livestock feed for ranchers who live in wine regions. So it seems odd that mixing a chemical herbicide with marc made the herbicide a more potent plant killer, but that’s what a group of French plant scientists found: the mix specifically increased the herbicide’s cell killing capacity. The herbicide in question is less toxic than many other agricultural chemicals, but strategies to use less of the stuff by augmenting it with a natural (and otherwise pretty darn safe) waste product are mighty appealing nonetheless.

None of these studies will win an Ig Nobel — for research that makes you laugh, and then makes you think — though Ron Washam recently had a few suggestions for MW thesis topics that just might, should anyone have enough chutzpah to take them up. Embarrassingly and disappointingly enough, the only instance of wine-related research or a wine-related researcher being granted an Ig Nobel was in 2005, when Yoji Hayasaka of the Australian Wine Research Institute was part of the team that won that year’s biology prize for carefully creating a catalogue of the smells 131 different frog species produce when they’re stressed. Enology is such an excellent repository of enjoyable, engaging, thought-provoking, and sometimes silly research; surely, we can do better…or worse?

DNA tests don’t do anything, or, how to read wine science news

Yesterday, a headline appeared in my email inbox, courtesy of Wine Business Monthly’s daily run-down, that read “DNA tests defeat wine barrel fraud.” About four different reactions crossed my mind more or less simultaneously.

1. I doubt it. Sounds like journalist hype.

2. Took them long enough; haven’t we had that technology for awhile now?

3. DNA tests don’t defeat anything. People defeat things.

4. Nifty!

I mightn’t have thought any more about it. But having spent the past week or two tearing apart assorted wine writings for evidence of how we make science happen in words, it seems I can’t just read anything anymore without asking: what do these words DO?

The headline is from a Wine-Searcher brief about new French technology to identify the geographic origin and species of barrel oak. But, really, the article is about the French asserting that they’re better than everyone else. The first three sentences of the piece outline, in very general terms, what the DNA tests do: researchers have genetically profiled enough oak trees to create a database against which new samples can be compared. Extract some kind of genetic information from tiny bits of barrel, compare that genetic “fingerprint” against the database and look for matches, and you’ve figured out where the oak used in the barrel originated.

I’m actually elaborating on what the Wine-Searcher piece said from general knowledge of how genetic testing works because the article spent its remaining 29 sentences describing how this technology fits into maintaining the cultural superiority of French oak over Hungarian oak. I’ve put it that way for a reason.

The DNA test itself might (maybe, in a very limited way) be value-neutral. But the way the test is constructed and used embodies the values of the researchers and the networks of interested industry members and funding agencies and organizations surrounding the researchers. The test determines geographic origin. Which geographies are important? Were American oaks included? We don’t know, because it wasn’t relevant, i.e. the French aren’t much worried about American fraud. How finely-grained do we want to make our distinctions in those famous French forests? The test isn’t value-neutral. The test is part of a network of people and organizations and values and priorities and economies and things. And in this case, the test has been enrolled in a program of asserting that French oak is both different and better than Eastern European oak. And that unscrupulous barrel makers are threatening consumers — and the integrity of the industry — by trying to pass off inferior stuff as the genuine article. So the headline actually is accurate (sorry, me #1 and 3), even if it left out some bits. The full version: “DNA tests” created by French researchers are enrolled in a program,  funded and commercialized by the leading French wine research institute INRA and the French Institute of Technology for Forest Based and Furniture Sectors (FCBA), “defeat wine barrel fraud” and increase the value of French oak.

But the article goes on to say that coopers aren’t so sure that this technology is useful after all. Barrels are complicated with many different pieces. Testing all of the pieces would be expensive and cumbersome. Not testing all of them wouldn’t necessarily prove anything useful about the barrel. The Wine-Searcher piece sets up the common dynamic: scientists say that new technology will help; industry people (coopers, here) say we’re not so sure. Maybe the coopers aren’t willing to be enrolled in that INRA- and FCBA-led program. INRA has decided that their participation doesn’t matter. Their own news release says, with certainty, that the test “will be an effective deterrent against fraud and will promote traceability measures with wood industry stakeholders.” Who’s right? Not really important. The important thing is the conflict. Everyone isn’t on the same page, which means that moving forward will be sticky.*

I’m not suggesting that the Wine-Searcher writers should have done things differently, though just a little more detail on the tests in that first paragraph would have gone a long way. It’s impossible to tell how much information these scientists and their tests can give us about a particular barrel: country-of-origin and species, or what forest, or what part of a forest? The headline overstates the case, but that’s journalism and readers know the genre: the title grabs our attention so that we read and figure out that the headline isn’t exactly true.

“Scientists craft DNA tests to verify wine barrel identity claims” — a more accurate headline — is cumbersome and less effective as an attention-grabber. If we want to be precise about it, we can say that the headline uses metonymy, a specific figure of speech in which a part of something stands in for the whole, more complicated thing. “DNA tests” stands in for “scientists who have developed and conducted DNA tests.” Cognitive linguistics says that metonymy doesn’t confuse readers; no one is running around out there thinking that DNA tests have evolved sentience and will be lobbying for the right to vote or applying for drivers’ licenses (I hope).

So if my point isn’t to call out journalists for promoting scientific inaccuracy — something I do often enough, but not today — what is my point? That words construct and reflect how we see the world. Wine researchers are plagued by the persistent failure of winemakers and growers and assorted other industry non-scientists to do what science clearly says is the right thing. We know that overhead sprinklers are a terrible way to irrigate grapevines in Eastern Washington state, so why are growers still using them? Why do people do wrong things against their better interest, even when they’ve been told that they’re wrong? First, because those industry non-scientists see pieces of their own complex networks that the scientists don’t/can’t/won’t see. They’re probably not being unreasonable (probably; everyone’s unreasonable sometimes); they’re working with different considerations. Second, because “science” is never just “science.” Science is always part of value-laden programs into which winemakers and growers and coopers may or may not want to be enrolled. The science isn’t just right; the science is part of an agenda. Third, because words make technologies real to people. We interact with ideas, scientific and otherwise, through words. Words tell us what ideas can and can’t do. And, in this case, words have helped criminalize Hungarian oak…and made a new French technology a good deal more limited and parochial than it might otherwise.

 

 

*The French have a habit of developing great, or at least new and complicated, ideas at the administrative level only to have them fail majestically at the implementation level because everyone else/the common people/the people actually affected by the technology saw problems the administrators never considered. See Aramis and the 1970’s attempt at French electric autobuses, among others. Or maybe everyone does this sort of thing and we just have a habit of noticing the French cases.

 

Nasty plastic residues in wine, elitism, and the real cost of an MW

I’d planned, today, to write about fine research led by Dr. Pascal Chatonnet and company at the French Laboratoire Excell demonstrating disturbingly high phthalate residues in some older French brandies, at least some level of plastic residue contamination in all of the French spirits and many wines they tested, and laying out some really sensible thinking on whether that’s a problem. But instead I find my hackles raised to unignorable degrees by one of the more insulting and ill-advised articles I’ve read on the wine-net recently (and it doesn’t even involve gender!) So here’s an effort to talk about the cost of an MW and plastic residues in wine, both.

From the things that make me spit fire file I offer you the following drivel by Ethan Millspaugh for Grape Collective. The title suggests that we’re talking about “the cost of becoming an educated wine drinker” — a fantastic and fascinating question — but the piece is actually about the cost of making an attempt at the coveted Master of Wine (MW) degree.

Mr. Gillspaugh massively underestimates that price tag at $25,000 (not including travel, not including wines for personal training, not including the time you didn’t spend working, not including babysitters or keeping the right society or purchasing a very good suit), and then suggests to us all that we don’t have to spend that much to become a wine expert. We could spend a very reasonable $60 to attend a WSET-hosted Champagne tasting or something (if, you know, you live in NYC or San Francisco or Chicago). Because really, that’s as good, isn’t it? And hence, once again, we have an opportunity for thoughtful and critical discussion on the internet sunk by smily faces and sheer lack of thinking.

The degree to which attaining the MW is limited to rich (white, preferably European, preferably English-speaking) people is hard to estimate. First, there’s the language issue. While the Institute of the Masters of Wine allows the written theory exam to be written in any language, everything else (study program, practical exam, thesis) is English-only. Then, the Institute headquarters and much of the training is in London, and its heritage is squarely British. And much as wine is becoming very international, it’s fair to say that the residents of some countries will be more interested in highly Eurocentric-trained wine specialists than others. I’m not willing to chalk the notable paucity of MWs in Africa up just to bias and barriers. Nonetheless, the entire continent has three — one in Egypt, two in South Africa, all in the most European of African countries — of 300 total world-wide, and two of those three are British ex-pats. Of five in Asia, only one is asian by nationality; the other four are caucasian and European- or American-born. The overwhelming majority of all MWs, of course, are British.

Scanning the member profiles on the Institute website, another striking thing is their limited range of occupations. Many are in the wine trade, either owning their own distribution company or buying for someone big. Many are self-employed consultants. A few are writers or “educators.” A few with technical backgrounds are now either buying wine or “consulting” in some non-technical capacity. In my thoroughly unscientific random clicking, I happened on not a single MW working in policy, public advocacy, or research.

Which brings me back to Chatonnet’s phthalate research. To put it briefly, the group found these common plastic additives — some of which are known endocrine disruptors that can mess with human hormonal systems — in most of the French wine and spirits they tested. Concentrations in 11% of the wines and 19% of the spirits exceeded accepted safety limits, with older spirits generally the worst offenders. Epoxy linings in storage tanks are the source; the solution is replacing old tanks with new phthalate-free ones or even retrofitting old tanks with a simple barrier coating — which they’ve developed, because that’s how awesome this team is.

Maybe the industry, now that they know, will get on that. But I hear from researchers over and over again that convincing wineries to heed such recommendations is one of their perennial banes. What if MWs were involved in helping to advocate for this sort of change?

What do MW’s have that PhDs in enology don’t? Highly public profiles. Broad, international wine industry knowledge. Extraordinarily strong networks. Often excellent communication skills (sporadic among scientists, unfortunately). Lots and lots of prestige. It’s really no mystery why MWs aren’t out leveraging all of those skills to improve awareness and policies around wine science and wine research. The MW is a general industry degree, not a technical one. MWs can earn much higher salaries elsewhere. All very understandable. I don’t want to believe that that has anything to do with the social elitism of being an MW, even if I suspect that it does.

And yet, what if — what if — someone decided to use an MW as a force for public good? I don’t have any specific plans or calls to action here. But with 300 exceptionally trained, driven, collegial wine lovers and more working up through lower levels of the pipeline, I’m sure someone has some ideas.

Why stuck fermentations are like Mad Cow Disease

Stuck fermentations — when sugar levels stop dropping and the winemaking process stands still — are one of the more persistently frustrating mysteries in winemaking. Like most winemaking mysteries, we understand part but not all of the situation. Bacterial contamination is one of numerous known causes of sticking: lactic acid bacteria can compete with wine for access to sugar, but it’s also long seemed that something else is going on. Researchers now have a better idea of what that something else is, and it involves prions.** Yes, prions, best known by nearly everyone as the infective agent in bovine spongiform encephalopathy, more fondly known as Mad Cow Disease.

Briefly, bacteria are producing some kind of small signaling molecule that provokes Saccharomyces cerivisiae to shift from preferentially fermenting glucose into alcohol to consuming other energy sources indiscriminately. Bacteria release the molecule, yeast take the molecule up and begin expressing a prion, and in some as-yet-unknown way, the prion jams the mechanism that normally tells yeast to consume only glucose when it has both glucose and other energy sources available. Bacteria don’t tolerate alcohol as well as S. cerivisiae, so it’s in the bacteria’s interest to get the yeast to make less of it. S. cerivisiae can use all manner of different molecules for energy, but a specific control mechanism ensures that it (usually) eats glucose first when glucose is around.

These findings tie into an overwhelming lot of very interesting, very intricate biology, the fullness of which is a bit much to discuss here. But (understanding that there are others), a few reasons why this research matters to scientists and to winemakers stands out.

To scientists:

  • Bacteria and yeast are talking to each other. Or, rather, bacteria are controlling yeast for the bacteria’s benefit. Bacteria produce lots of small messenger molecules — a bit like hormones in the human body — to communicate amongst themselves. But the idea that they use a similar molecule to control the behavior of a different species is exciting. Bacteria probably do this all the time, too, but microbiologists are behind on learning about it because we traditionally study one type of microbe at a time, by itself, in a test tube or beaker. Imagine studying 12 year-old boy behavior by putting lots of 12 year-old boys in a room by themselves and watching them for a week. That’s what we’ve been doing with bacteria. Microbiology as a field is increasingly realizing that there are better ways (which are, of course, more complicated, and therefore harder…)
  • The mechanism involves prions, which are cool because they’re a relatively recent discovery and we’re finding them in places we didn’t see coming. It’s still not clear how they’re working in this setting, but finding out will almost certainly involve learning some new and interesting biology

To winemakers:

  • Winemakers who are adamant about avoiding stuck fermentations are probably also vigilant about trying to keep bacterial contamination out of their wines, so I imagine this news doesn’t change much. Nonetheless, some folk might end up using more sulfur dioxide in an effort to knock down bacteria in ferments that tend toward stickiness.
  • More interestingly, researchers may be able to develop yeast that don’t respond to the bacteria-induced switch, maybe with a mutated form of the prion protein. Non-stick yeast?

**The research is published in two complementary papers (here and here) in the journal Cell and, as happens with particularly interesting stuff like this, the editors have put together a short summary. It’s still pretty dense stuff unless you have a background in molecular microbiology, but you can find it here if you’re interested in the details (and if you have institutional access to the journal).

Sustainability at New Zealand’s Bragato conference: what’s next?

The Romeo Bragato conference is New Zealand’s national wine industry conference for producers, policy makers, vendors, researchers, and such (and today, “such” even included New Zealand’s prime minister). With that audience, the topics discussed are broad, which makes it particularly interesting that the word “sustainability” seemed to crop up more often than any other today.

The main message from many today — growers and winemakers and administrators — is that New Zealand is awesome and needs to shout about it a bit more loudly. It’s hard to disagree. 94% of the country’s wineries are certified through the Sustainable Winegrowing New Zealand program (“swins”). 94%! And yet, to me, that’s actually a lot less significant on a story level than the individual, often very thoughtful initiatives wineries and vineyards are taking beyond that certification. From a consumer perspective, it’s near-impossible to translate the soft language on nzwine.com/sustainability into something meaningful and tangible; “foster biodiversity” and “monitor and manage erosion risk” and “engage in clean production practices,” as the sustainability standards say, is all pretty soft soap. But when I hear that Yealands Estate in the Awatere Valley is baling their vine prunings (yes, like hay) and burning them to fuel boilers that supply most of their hot water needs and eliminate the need for about $100,000-worth of LPG per year, that’s meaningful. That’s tangible. So are things that don’t involve metrics at all, like sniffing fine-aged manure with Rudi Bauer on his biodynamic estate in Central Otago; whatever you think of biodynamics, his extraordinary care for his land and vines and people is, well, something you can practically taste. Nevertheless, while I think folks abroad tend to think of New Zealand as a near-untouched refuge of pristine greenness (not entirely true, regrettably), the fullness of what Kiwi winemakers have achieved together on the sustainability front doesn’t come across as it should. Kiwis tend to be a pretty understated bunch, and it came up several times today that they may not realize how extraordinary, and how absolutely worth talking up, “just the thing we do here” really is.

But a second message — the step most speakers take after patting their collective backs — is the what’s next question. We’re great, but we can do better. And not just we can do better, but we must do better, and fast, not so much to protect our land as to protect our edge over those wilily Chileans who could rapidly and easily overtake us if they can market their wines as being more sustainable than New Zealand’s.

So what’s next? The industry has just updated and stepped up their sustainability reporting tool, WiSE (part of the Sustainability Dashboard project through which part of my PhD research is being funded), which is intended to be not just a reporting but a benchmarking and self-improvement tool. But that doesn’t really answer the question. The New Zealand wine industry has been remarkable in collaborating to create a unified international image. Seriously: where else can you find 94% certification in any non-mandatory administrative scheme? What’s the next direction in which the industry, collectively, will choose to travel?

Gwyn Williams, the chair of the New Zealand Winegrowers Sustainability Committee and a man with 31 years of Kiwi vineyard-managing experience, thinks that the national wine sustainability movement has stalled. I wonder if that stall is because there isn’t clear consensus on what’s next. Organic Winegrowers New Zealand is aiming for 20% certified organic vineyards by 2020. The president of that organization, James Milton (also the winemaker at the Demeter-certified biodynamic Milton Estate in Gisborne), said today that the organic and biodynamic folk need to work harder at speaking the languages of sustainability and science instead of isolating themselves in their own strange little corner as they’ve traditionally been wont to do. But, in a later session also on sustainability, Chris Howell of Prospect Vineyard in Hawke’s Bay mentioned being unconvinced about the totality of organic practices from a science perspective. A walk through the vendor’s area made it obvious that he’s not alone.

Is organic the next step beyond “sustainable?” Or biodynamic the next step beyond organic? Or organic-with-caveats — organic, but we’re not certified because we do X when we really have to, as I hear many vineyard managers say? Or just raising the bar on those key performance indicators about which the sustainability folk are always talking? More and better of the same, or something new?

If the New Zealand wine industry can decide, together, what better-than-sustainable looks like, they’ll achieve it. They don’t talk very loud, and they’re the most collectively laid-back people I’ve met, but I’ve learned in the past nine months not to underestimate the extraordinary Kiwi capacity for getting the job done.

“Fit-for-purpose” yeast from the AWRI

The Australian Wine Research Institute (AWRI) has created a quick-read summary page on their ongoing project to develop “fit-for-purpose” yeast: yeast strains designed to facilitate specific flavor profiles for specific applications. They’ve already developed and released (through AB Mauri and Anchor) several strains including two interspecies hybrids — Saccharomyces cerevisiae crossed with S. kudriavzevii or S. cariocanus — and low H2S-producing strains. More are being tested in Shiraz and are likely to emerge over the next 3-5 years. The AWRI is making a point that this research is Aussie-focused — their argument is that similar work being done elsewhere is creating yeasts not necessarily suitable for Australian wine styles — but no doubt their results will end up helping non Australian-industry levy payers, too. It’s worth noting that their development strategies rely on good old traditional genetics strategies and not genetic engineering. They’re not inserting genes from other species into yeast; they’re breeding different yeasts together, encouraging yeast to mutate (that is, spawning lots of random changes in their DNA with chemicals and stress) and looking for useful mutations, and using contemporary genetics to understand which genes do what. For a quick explanation of why I’m glad that they’re sticking with traditional genetics strategies instead of creating GMO yeast, check here.

Whether you’re excited about the prospect of using tailor-made yeast to target particular flavors or whether you’re in the don’t-inoculate-my-wine camp and hold that fermenting with yeast from the environment is the only or best way to terroir-full wines, it’s hard to argue that knowing more about yeast is a bad thing. Developing new commercial products may be an increasingly major research driver as scientists need to look for support from private sources. Furthermore, ending up with a new product you can hand to someone is a tangible way of saying, “Here, look; our research really is applicable and relevant to real-life winemaking!” Regardless, projects like these continue to provide an umbrella for basic research on yeast genetics and wine flavor development. And maybe not tomorrow, and maybe not next year, but in the long run, that’s something that ends up helping everyone.

Does adding tannin boost aromatic thiols, too? It just might.

Thiols aren’t quite like bacon, but they’re not too far off trend-wise. These aromatic sulfur-containing molecules are highly appealing in small quantities — even low concentrations lend a wine’s aroma fresh fruity notes (tropical in sauv blanc, black currant or berry in reds). Just about everyone wants them, or wants more of them. They’re at work in the expected places (thiols in sauvignon blanc are like the bacon in your pasta carbonara; bland without, and much better with), but also do a fair bit in the unexpected ones, too (thiols contribute to the aroma of Bordeaux reds and Provençal rosés, for example, and bacon, I’m told, does excellent things to cupcake frosting*).

Unlike bacon, we still don’t have an especially good idea of how thiols are formed (we figured this out for bacon a good long while ago, I believe). The amounts yeast transform from various precursors under realistic wine conditions just don’t add up to the final concentrations we find in wine, and how the rest happen remains an open question. Last year’s news was that tannins contain thiol precursors upon which yeast act during fermentation. Now, those researchers (an Italian group, with the aid of a Sauvignon blanc-oriented researcher from New Zealand) have demonstrated what I’m sure they’d hoped for when they published last year’s paper: adding tannins to wine before fermentation increases a wine’s thiol concentrations, specifically 3-mercaptohexan-1-ol (3MH). (For some context on 3MH and other sulfur compounds, Jamie Goode’s blog article on the topic is a good primer).

This study is very much a first step, and a bit of a disappointing one. Tannin was only added at one concentration: 1.6 g per 2 kg batch, compared with a no tannin-added control. Seeing a dose-dependent response — add more tannin, get more thiols — or showing that the relationship between those two variables isn’t linear, anything other than just two points, would have been much more convincing. As would using larger than 2 kg batches for those experimental wines (2 kg ~ 1 750 mL bottle), since the volumes in which experimental wines change yeast fermentation and oxygen exposure dynamics; the oxygen mightn’t be relevant here, but the fermentation parameters are. AND, each wine was only made in duplicate, not satisfying the usual experimental expectation of performing studies in triplicate. With two samples, if one is off you can’t tell which reflects the trend you’d see if you did the experiment a hundred times (and you certainly shouldn’t just average them together); if three samples all group, you can feel better about life (and your results). AND, with so little wine, the authors couldn’t conduct a proper sensory analysis, not that doing so would have been worthwhile in any case with their mini-make-do winemaking technique. In other words, this study is less than convincing on methodological grounds.

All of that said and duly noted, this study points toward some interesting possibilities. For instance, I’ve recently talked with a few winemakers who have been experimenting with tannin additions to good but confusing effect. (I seemed to come across people talking about tannin additives about as often as I did bacon-laden menu items on my most recent trip through Eastern Washington, which is to say, a lot.) They know good results when they see them, and they like what they taste. But tannin assays sometimes seem to yield results that conflict with experience, with the assay saying that the with-addition and without-addition wines contain the same amount of tannin even though the winemaker can taste a difference. All manner of possible explanations exist for that phenomenon, and I don’t want to suggest that thiols are responsible for those sensory differences. Nevertheless, this study is a good reminder that adding anything to wine is bound to have more than just one obvious, direct effect, and that adding tannins could play with wine aromas in ways we hadn’t expected.

*I’m told, because I’m one of three people on the planet who likes neither bacon nor cupcake frosting.