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.

Pairings with pinots and the futility of looking to science for answers

I have a horrible (given my current location) admission to make: Central Otago pinot noir is, to date and as far as I can tell, not my favorite thing in the world. That said, Otago pinot noir is lovely and fulfills a completely different function at table. One of the best meals I’ve ever had with an Oregon pinot was the whole salmon I roasted with a bunch of herbs and various alliums for my last Thanksgiving in the States. A guest serendipitously brought a Lange pinot, and it was memorable. On the other hand, Grasshopper Rock’s example — grown on the Clutha River in Alexandra, Otago — didn’t really grab me on its own, but was just lovely when I tried it alongside some smoked hoki that I’d brought home from the Auckland fish market (yes, in my backpack, on the airplane). Those rather robust smokey flavors emphasized the wine’s structural and savory notes and took the focus off cherry flavors that were a bit more candied than I prefer.

What I just offered you is a lay theory. To make it more than that, I’d need an empirical study or three to examine the interaction of smoky foods with various potential sensory qualities found in pinot noir. The problem with that idea, apart from it having nothing to do with my current main priority, i.e. the PhD, is that food and wine pairing research is obnoxious. .

Food and wine pairing articles (I’m quoting this one) are full of statements like this: “This research found that eating cheddar cheese before drinking Shiraz reduced some of the negative characteristics of the wine and enhanced the preference for the wine. This indicates that consuming food and wine together can minimize some of the less desirable flavors of both.” And hypotheses like this one: “Certain food and wine combinations will be perceived as significantly better than others.” The latter of which, I suppose, points out that food-wine preferences could be completely personal, like favorite colors (except that favorite color preference isn’t random, either).

Perhaps this sort of research really interests sommeliers who could think about the benefits of a shiraz and cheddar pairing in a tasting menu, though I doubt they need reassurance that their choices will work for someone other than just themselves. The question still arises: is science, in all its reductionist glory, really the best way to attack food and wine pairings?

First, let’s get a methodology point out of the way. Apparently, the best way to evaluate food and wine pairings is to ask people to eat and drink at the same time rather than, say, munching a bit of cheese, swallowing, and waiting thirty seconds before taking a sip of wine or vice-versa. Because that’s the way people usually eat.

Moving on. Research to date says that wine sweetness and astringency, but not its acidity, are significant in determining ideal food pairings. The most recent food-wine pairing article I’ve encountered tried to suss out whether acidity was in fact important, and the role of wine expertise in food-wine preferences, along with moving beyond many previous studies by pairing wine with foods other than cheese. The chosen foods? Chevre, brie, salami, and milk chocolate, paired with an Ontario chardonnay, an Ontario sauvignon blanc, an Argentinian cabernet sauvignon, and an inexpensive LBV Port. Needless to say, this study isn’t going to give me any insight into my pinot noir pairing theories. Or, for that matter, any insight into any real food and wine pairing conundrum anyone ever faces anywhere.

I’m poking fun, but I’m not being wholly fair. The authors of this article have more expertise in what they’re doing than I do. It’s obvious to any wine or food nerd which of the above pairings will and won’t work, but that evidence is anecdotal, not scientific, and maybe those assumptions are worth testing. But when the authors begin asserting that this study provides evidence that acidity, sweetness, and tannins are all important in pairings, just from showing that milk chocolate works better with port than with chardonnay? No. Four examples aren’t enough to allow for that conclusion, not near enough to weed through and rule out all of the other things (confounding factors) going on in both the wines and the food.

So we’re back to where we started with pairing food and wine. What says our weight of accumulated, non-scientific wisdom? And does it taste good? The reductionism of sensory science may have useful ways to tackle the hyper-complexity of food + wine (don’t ask me whether that’s more or less complex than, say, the human immune system, which science seems to tackle with at least some success), but I’m not sure they’ve figured them out yet. And when I’m trying to decide what to serve with my next glass of pinot noir — Oregon, Otago, or otherwise — the only research I expect I’ll do will be on my favorite cooking blogs.

**All sorts of other fascinating alternate-scientific approaches have been taken to food and wine pairing, Chartier’s fascinating Taste Buds and Molecules: The Art and Science of Food, Wine, and Flavor being perhaps the most interesting example. What I’m talking about here is the mainstream pairing science found in peer-reviewed journals.

Measuring not just tannin concentration but tannin behavior: Kennedy’s stickiness assay

Why does it always seem that we know the least about stuff that’s the most important? Tannins garner a lot of wine researcher’s attention, and for good reason. No one needs convincing about how important tannins are to wine quality (especially not the consulting companies who’ve correlated high tannin concentration with high wine magazine ratings). The amount of noise made about tannins, though, could give someone seriously inflated ideas about how well we understand them.

Excellent wine chemists are, in fact, still thinking about really good, consistently accurate, and every-day-practical ways of measuring a wine’s tannin concentration. The well-known Harbertson-Adams assay went a long way in that direction, but isn’t the last word on the topic. But just looking how much tannin a wine has doesn’t tell us enough. “Tannin” describes a whole group of molecules, and those molecules behave in different ways.

What we really need is a way of measuring not just how much tannin a wine has, but how astringent it’s likely to feel. That’s a tall order — astringency is a complicated sensation affected by alcohol concentration, sugars, polysaccharides, the person doing the tasting, and undoubtedly other factors. Just tasting the darn thing is, without question, the most elegant and reliable way to measure wine astringency. But it would still be useful to have a way of measuring the relative astringency of different types of tannins to correlate with how different production techniques affect those tannins and make some predictions. And, just as importantly, if we’re ever going to figure out what tannins do, how they behave, and how astringency works, having more tools to look at them is important.

James Kennedy’s group at Fresno State is working on a way to go beyond traditional tannin measurements, which just tell you how much tannin you have, to develop analyses to tell you what the tannin you have does and how it’s likely to produce astringency. More particularly, they’ve developed a way to measure the stickiness of any particular type of tannin molecule. Stickiness, as defined in the article, is “the observed variation in the enthalpy of interaction between tannin and a hydrophobic surface.” Or, to put it a lot more simply, stickiness describes how strongly a tannin is inclined to attach itself to something else (without actually reacting with it). This seems pretty commonsensical — if we sense astringency when tannins glom together with our salivary proteins, then we’d like to know how glom-inclined those tannins are. They’ve shown that their stickiness measurement for a particular set of wine tannins remains constant no matter how much of the tannin you test — in other words, they can measure stickiness as a tannin quality, not tannin quantity.

It’s a trickier puzzle than it might seem. How do you measure how tightly two molecules are holding on to each other? And when you’re interested in how different tannins interact with proteins, which are themselves a very diverse group of molecules, how do you choose which protein is going to be the protein that represents all other proteins?

For Kennedy and company, the solution involved choosing something that isn’t a protein at all but polystyrene divinylbenzene, a polymeric resin that holds on to tannin in remarkably the same way as the specific amino acid (proline) that acts as the tannin-attractant in salivary proteins. The resin allows for a standardized stickiness measurement and no doubt has all sorts of advantages in terms of working with it in the lab. It won’t actually behave like real salivary proteins which, being folded up into various shapes with proline more or less accessible along their various crannies, don’t bind tannins in ways so predictable. The upshot is that this is a standardized measure of stickiness (a defined scientific parameter), not an actual measure of astringency (a subjective sensation). Nevertheless, stickiness values and astringency should be related in predictable ways. We’ll very likely see a publication verifying that relationship with human tasters before too long.

Stickiness assessment involve some fairly complex chromatography, improving on a method the lab published last year. The methodological details are less important than realizing that this isn’t something that even a well-equipped winery lab is going to be able to do on their own (unlike that Harbertson-Adams assay, which is pretty accessible for a lot of winemakers). Though some wineries may measure tannin concentrations with that Harbertson-Adams assay, which is pretty accessible for a lot of winemakers, stickiness measurements aren’t going to become the new best thing in figuring out how long your syrah needs to spend on its skins before being pressed off. Too expensive (the chromatography columns needed for this kind of work run hundreds of dollars each), too training-intensive (unless you have a chemistry grad student hanging out in your winery), and too little of an improvement over just tasting the darn thing. This research isn’t likely to change the way anyone makes wine tomorrow or even for the next year or two. But it very well may change the way scientists study and think about tannins, the kinds of questions they can answer — those tricky issues around the relative astringency of various seed and skin tannins, for example — and what they can tell winemakers about targeting specific wine styles a few years down the road. And that’s worth making some noise over.

 

Why do yeast make alcohol?

Ever wonder why yeast make alcohol? Probably not, I realize, but you should. Yeast throw off ethanol in the process of metabolizing sugar, so alcohol is a byproduct of survival; fair enough. But alcoholic fermentation is, in fact, a surprisingly inefficient way to get energy. The standard oxygen-requiring way of breaking down sugar used by most cells, our own included, wrings somewhere between 30 and 38 ATP (38 is the ideal number; it’s probably never quite that high in practice) out of a single glucose molecule. (ATP is the cellular currency in which energy is transferred and spent.) Nevertheless, alcoholic fermentation has the distinct advantage of not needing oxygen and so it makes perfectly good, intuitive sense for Saccharomyces cerevisiae to use it when oxygen isn’t available.

Here’s the quirk: S. cerevisiae uses inefficient alcoholic fermentation even when it does have access to oxygen, even though it has the machinery for the much, much more energetically worthwhile aerobic metabolic process. Yeast will only switch to aerobic metabolism when the amount of sugar available for them to eat is very low. Why? A good question, and one microbiologists haven’t had much success answering.

Our best hypothesis according to a brand-new review on the subject comes in two parts:

  1. Alcoholic fermentation lets yeast act fast to use up the “public goods” while squirreling away private resources for later. Every microorganism you’ll encounter in grape juice can consume sugar. Very few can also consume (and get energy out of) ethanol, but yeast can. So, by converting sugar to ethanol, S. cerevisiae can starve out other microbes and leave itself with a food source for later.
  2. As an additional and maybe even bigger benefit, ethanol is toxic to most yeast and bacteria at concentrations that Saccharomyces can tolerate with relative ease

Possibly the most bizarre thing? We don’t know much about what determines the circumstances under which S. cerevisiae, our long-time compatriot and coworker, produces alcohol versus making energy in some other way. We’ve looked at when and where different yeast genes are expressed and when and where it makes different byproducts but, like so much else in the wonderful and frustrating world of modern-day genetics, putting together the whole story is still a work-in-progress.

White grapes: more colorful than you think

Our society has a bizarre habit of mislabeling things by color. The familiar case in point: white people are never white but always various tints of pink, peach, and yellow; black people are invariably not actually black but some shade of brown or tan. Less familiar case in point: white wines are really always somewhere in the yellows, and the grapes themselves range from green through yellow to pink. (Red wines are, at least, red, even if the grapes which give them birth are more aptly blue, black, and purple).

We do talk about the color of white wines, from the pale straw of a light-bodied sauvignon blanc to the amber of an elderly riesling. Anything not firmly lodged on the green-yellow to brown-yellow spectrum, though — including forays into pink — is considered a fault. Now, that judgment (like some other “wine fault” decrees) seems a bit arbitrary to me: would I really mind sipping a pinkish chenin blanc? (No, I would not). But “pinking,” as it’s called, is a problem, if for no other reason than consumers might have a hard time coming to grips with it. Gewürztraminer grapes are unquestionably (and beautifully) pink, but gewurztraminer isn’t one of the grapes prone to pinking and, in any case, we’re not talking about color derived from skin contact — those wines are “orange,” not pink. Real pinking qua pinking can show up before bottling or suddenly after pouring and seems to be the result of exposing a reductively-made wine to oxygen.

A group of chemists from Portugal have done a convincing job of demonstrating that — at least in the Siria grapes they tested — pinking is caused by…anthocyanins. Yes, the very same pigmented molecules that make red wines red. But, what are anthocyanins doing in white wine?

In some sense, they were there all along. All grapes have the genetic machinery to be red. White varieties are mutations, the result of genetic changes in the genes responsible for the production of red anthocyanin pigments in grape skins. The same mutations seem to exist in all white grape varieties, which suggests that they probably all descended from a common ancestor.

Anthocyanins would seem the obvious culprit for pinking, even if it does seem odd to think of them being found in whites — that genetics of grape color research isn’t especially new. One of the classic wine science textbooks, Ribéreau-Gayon and company’s Handbook of Enology, says that pinking is caused by unknown compounds that can’t be anthocyanins because they don’t respond to sulfur dioxide and pH in the expected ways. That book was published in 2006, though, and folks like James Kennedy at Fresno State University and Jim Harbertson at Washington State University (along with a good many other researchers) have, since then, made a fair bit of headway into figuring out how anthocyanins react with each other and other wine components. (It remains a terribly complex and incompletely understood topic.) This team of Portuguese researchers could still observe that the pinking-related anthocyanins they observed didn’t act exactly like “normal” anthocyanins because they polymerize over time in the wine, which makes them more resistant to the color-bleaching effect of sulfur dioxide. Suffice it to say that they go through some complicated chemical acrobatics to show that the molecules they isolate from their pink Sirias are indeed anthocyanins.

The researchers responsible for this study speculate that Siria, the rather obscure Portuguese white grape variety with a persistent pinking problem that they chose to examine, may have regained the ability to manufacture some anthocyanins. Not enough to make the grapes overtly pink in the vineyard, but enough to belie their presence after at least some kinds of winemaking operations. (Anthocyanins are unstable molecules susceptible to changing in the presence of oxygen and other molecules.) Though they haven’t substantiated that speculation with molecular analyses, it’s not out of the question that additional mutations in those anthocyanin-producing genes might restore some of their functionality or cause them to be transcribed under specific circumstances.

If you’re not a winemaker with pink problems, why is this research interesting? It’s a good reminder that white grapes aren’t necessarily simpler than red ones, as it’s so easy to imagine, and that we’re still learning a lot about the very complicated pigments that make wine color happen. But it also makes me stop and think about how flexible plants really are. We can select for and preserve features we want through careful clonal selection of the most highly desirable plants, but vines are still going to change and mutate and do new (or redo old) things on the sidelines.

Will magnetic yeast make better Champagne?

UPDATE: Deborah Parker Wong has written a detailed discussion of magnetic yeast technology and its implications for the Champagne and sparkling wine industries for the September-October 2014 edition of Vineyard and Winery Management in which she makes it clear that I’m wrong about #3 below: at least some traditional producers are enthusiastic about rapidly making use of the new technology. The full text of Wong’s article is available for free via her website.

Wine Searcher ran a story this past week about new technology from the University of Ljubljana that speeds traditional sparkling wine processing times by magnetizing yeast cells. Magnetic nanoparticles affixed to the cells’ surface don’t interfere with fermentation and let winemakers literally and near-instantaeously pull the yeast into the neck of the bottle by applying a magnetic current. Since riddling — slowly inverting and rotating bottles to remove (unattractively cloudy) dead yeast after the secondary in-bottle fermentation responsible for effervescence-generation — traditionally takes a few months and a LOT of hands-on work, a 15-minute flip-a-switch solution looks pretty attractive. BUT:

Interesting fact #1 – This technology isn’t new, though applying it to the sparkling wine industry is. Bioengineers came up with magnetic yeast in 2009.

Interesting fact #2 – If actually adopted by the industry, magnetic yeast will be far from the only use of nanoparticles in food. Quite the contrary, which you know if you follow the American health and science news. Titanium dioxide nanoparticles are common additives to everything from chewing gum and toothpaste to yogurt and soy milk, generally to the effect of making whateveritis whiter. Nanosilver particles are common both as agricultural pesticides and in antimicrobial coatings for household goods, and nanolipids and nanoproteins and assorted other nanostuff finds its way into all manner of food-related items. The consensus is that we don’t yet have a consensus on whether and to what degree ingesting nanoengineering is safe (a peer-reviewed take on that question here; a more accessible and more inflammatory story from Mother Earth News here). Logically, magnetic force should effectively pull all of the magnetic particles (made from magnetite, if the Ljubljana authors are using the same general strategy published in the 2009 paper) out of the wine, but nothing is perfect. If residual particles remain, drinking them might be a health risk, but it won’t be a unique one.

Interesting fact #3 – Alright; this one isn’t a fact. It’s a speculation based on fact. I speculate that we needn’t worry too much about magnetite in our celebratory libations. Champagne in particular and high-quality, methode champenoise sparkling wine in general, is not about fast. Exactly the contrary. Champagne legally has to spend at least 15 months in bottle and at least 12 months on the lees, and usually exceeds that by a year or two because age on the lees is vital to the flavor profile of high-quality sparkling. I reviewed some of those considerations in this article for Palate Press.

The problem with riddling isn’t the time per se so much as the labor: some poor guy has to spend his days jiggling bottles (and if champagne riddlers don’t have a high incidence of occupation-induced carpal tunnel syndrome, I suspect that it’s just going undiagnosed). The gyropalette solves that problem by loading a box full of bottles onto a modified forklift and letting the machine jiggle them for you. That bit of technology has been popular and successful, but it seems to me that it’s also a lot less expensive than magnetic yeast.

Think about it. Yeast reproduce in the bottle, a lot. So, every yeast cell used in inoculation needs to be loaded with magnetite particles to ensure that all of its many, many offspring has at least one magnetite particle.** Don’t even think about generating your own yeast innoculum. And that’s before we get to the magnetic set-up to actually pull down the yeast. I don’t know. Storing wine (and paying that poor guy) is expensive. Maybe this is a cost-effective solution. But if high-end producers aren’t going to be seduced by speed, and if lower-end producers are disinclined to spend more money on production technology, and if the wine industry in general tends to be stuck in the mud, I suspect we needn’t worry too much about drinking magnetite anytime soon.

** Maybe effective clarification doesn’t require that every yeast cell be magnetic, if the yeast tend to stick together (flocculate) and magnetic cells will help pull down their non-magnetic neighbors. Without reading the paper I don’t know, and since I can find neither the paper (maybe it’s not yet been published, or maybe it wasn’t published in English) nor the specific names of the researchers nor any other mention of the research on the University of Ljubljana’s website I have to speculate. It’s disturbing that I can’t find another source backing up the Wine-Searcher article (and I don’t personally know it’s author and can’t locate him via the usual tricks) but, then again, I don’t read Slovenian.