Fermentation caused by living things? Balderdash!

Small Things Considered is the very endearing blog of the American Society for Microbiology and, like all microbiology, it occasionally touches on alcoholic fermentation. This week, Elio unearthed a hilarious spoof from the early days of fermentation science. Two acclaimed chemists (Justus Liebig and Frederich Wöhler published it in 1839 to make fun of their competitors’ obviously stupid notion that living microorganisms are responsible for the process of fermentation — really, what self-respecting chemist could believe that nonsense! Their imaginings around what those microorganisms might be doing is made even funnier by how close they came — entirely by accident — to the truth. It’s a good laugh, but it’s also a good reminder that so much of what seems patently obvious seemed patent nonsense to our predecessors…and that it can be hard to tell what parts of what we know today might well be balderdash in another hundred years.

“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.

(More) Race, class, and gender in wine writing

Eminent wine blogger Tom Wark is being provocative again (if you know Tom, I’ll wait for your shock and awe to subside, and if you don’t know Tom, that was sarcasm) and poking at several attendees’ comments that speakers at the recent 2014 North American Wine Bloggers Conference* were overwhelmingly male. Tom’s original post is less interesting than the comment thread — sincere congratulations on that, Tom. I chime in with a reminder that critical awareness of power structures is a non-stop job.

I don’t have an answer to the problem of discrimination, Tom; if I did, I should darn well be sharing it a little more aggressively. But I can say that the answer to “why aren’t there more women speakers at WBC?” or “what should we do about it?” begins with awareness that power structures exist. And that, fundamentally, the answers boil down to what I tell my composition students when they ask me nearly anything: 1. What is your purpose? 2. Be aware of what you’re doing.

*I wasn’t there for obvious reasons, i.e. being in grad school on the other side of the world.

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.

On Palate Press: What Jane Goodall taught me about wine science

With so much interesting research, so many papers published, so many nit-picky little things to remember about temperatures and acidity and bugs and the rest, it’s easy to lose the forest for the trees in enology. When the much-beloved chimpanzee expert Jane Goodall came to visit the Centre for Science Communication that I call home about a month ago, in talking about the African forests she actually reminded me to step back and look at the metaphorical enological ones, too. Maybe studying chimps isn’t all that much like making wine, but I’m not sure they’re that different, either: technology and training can get in the way of both, and stories win people over more than arguments whether you’re talking primates or pH. The full story of what Jane Goodall taught me about wine science is here on Palate Press. 

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.

 

Toward better wine science communication (and my PhD)

If you’re a winemaker, a vineyard manager or viticulturist, or in a similar role, and if you have ten minutes to help a PhD student gather some data (and improve the state of research communication in the wine industry), I’d be most grateful for your response to this survey on your feelings about winemaking and growing information and where you go to find it. Find the completely anonymous survey here: http://fluidsurveys.com/s/winescienceinformation/

Pro-alcohol research and improving wine science communication, one PhD at a time

Yesterday, Tom Wark snarked off (I mean that nicely, Tom) about “alcohol ‘researchers'” who seem to think that wine, beer, and spirits are social evils to be restricted and discouraged as much as possible. I’ve read plenty of papers that appear to start (and finish) with that agenda, but not all “alcohol researchers” are anti-alcohol. In fact, you could call me an alcohol researcher.

More properly, I’m a wine science communication researcher. (Yes, I know that that’s a mouthful.) While at one point I researched the microbiology of wine production, I now look at how wine research information moves around the industry among scientists and writers and winemakers and growers (and sometimes even consumers). I’m trying to understand how scientific ideas about winemaking and growing come to exist in the industry. When science moves from a peer-reviewed scientific article to a trade magazine, what changes? What can those changes say about how we can better design experiments and better communicate their results. Of course, I can’t say how all of this communicating is important if I don’t know what winemakers and growers are reading and using — and, to my shock, no one seemed to know (if they do, they’re not telling). So I’m also investigating how winemakers and growers navigate the morass of resources available to them: what they read and listen to, who they talk to, and their frustrations about the process. If you’re a winemaker, vineyard manager, or someone in a similar role, you can help me out by taking ten minutes to complete a short survey around those questions. (The link is also tacked to the top of this blog). Finally, I’m writing a popular (that is, not academic) book about how the story of wine is also the story of the sciences, from physics to medicine and everything in-between. More on that later.

I probably don’t need to argue for why wine is worth researcher’s time as a public good to promote instead of a social ill to eradicate, but it’s good to note that it’s fundamentally about humanity as much as science. Wine is a food nourishing to body, mind, and spirit when taken in appropriate quantities. It’s also a cultural icon and a historical treasure. If you want to talk to me about restricting wine because too much alcohol can kill you, your agenda had better also include restricting access to and advertising of butter and cheese — because too much saturated fat can kill you — and honey and jam — because too much sugar can kill you, too. Then show me your thoughtful plan for accommodating the essential cultural and social roles that all of those foods play around the world.

My research is aimed, at the biggest picture level, at making scientific research more efficient, but it’s also about helping people make better wine by improving the information available to them. Besides, when getting a PhD involves wine, science, and writing — and rhetoric, and philosophy, and talking to winemakers, and trying out living in New Zealand — it’s hard to see how things could be much better.

 

Rippon’s Gewürztraminer and the quandry of white wine fermentation temperatures

I opened a bottle of Rippon’s lovely 2011 Gewürztraminer a few nights ago in a small act of celebration upon having an academic manuscript accepted for publication (hooray!) As I bathed my nose in pretty peach and lime and rose notes, to my surprise, my very non-oenophile husband commented that he didn’t find it very aromatic. (I blame the tahini-miso oca, or New Zealand yams if you prefer, that he’d just noshed). Conversation ensued about white wine aromas. Conversation turned technical, as it’s inclined to do around our table (he may not be an oenophile, but my partner is unmistakably an academic and a knowledge-hound), and an interesting conundrum turned up.

Modern winemaking dogma says that white wines should be fermented at fairly cool temperatures to maximize their aromaticity. Aromatic molecules are, by definition, volatile — they can leave the liquid and travel into the air, where we can sniff them into our nostrils and bring them into contact with aroma receptors. Fewer of those volatile molecules will leave the liquid at cool temperatures than at warm ones because (to simplify), warmer molecules have more energy, are moving faster, and consequently have a better chance of flying off the liquid’s surface. Fermenting at cool temperatures, then, keeps more aromatics in the wine for you to enjoy on a later occasion rather than liberating them into the atmosphere of the winery.

Fermentation creates heat, sometimes even enough to kill off the yeast and stop fermentation in mid-stride. To keep that from happening, winemakers have a few different options. Smaller containers have higher surface area to volume ratios than large ones, release more heat into the surrounding air, and generally stay cooler. The old-fashioned solution, moving small tanks or barrels outside to take advantage of cool night-time temperatures, can work for small operations in cool places. Keeping the room where fermentation is happening cool helps, though that’s a pretty inefficient and energy-expensive option. Far and away the standard contemporary solution, the jacketed stainless steel tank, lets cellar staff dial in specific temperature programs and is near-ubiquitous in modernized operations of decent size. Near-ubiquitous, but not entirely so. Two of my favorite wineries near my old home and my new one, Eyrie in the Willamette Valley (an Eyrie pinot blanc would have been on my celebratory table if I’d had any) and Rippon in Central Otago, both do without. They’re expensive, and they also don’t fit with the low-manipulation philosophy both espouse.

So here’s the quandry. Both Eyrie and Rippon turn out deliciously aromatic whites. Neither uses sophisticated temperature control during fermentation. Both McMinnville, OR and Wanaka, NZ are coming on cool roundabouts harvest time and both operations use small tanks, but it’s still safe to say that those ferments are exceeding the UC Davis-endorsed temperatures.

Why don’t they (and every lovely white wine made before the advent of modern refrigeration) seem vapid, empty, and unappealingly burnt out? I can’t be certain. When I asked Jason Lett, winemaker at Eyrie, this question, he suggested that I do an experiment to try to find out. Having left my lab days behind me, I’m not in a position to do so (it would be a big project in any case) so I’m left to speculate.

The situation is too complex with too many variables for me to evaluate with any chance of accuracy. Yeasts produce different arrays of aromatic compounds at different temperatures, for example. But I also speculate that these wines would, in fact, be more aromatic if they were kept cooler. They don’t seem to be lacking anything, I suspect, because spontaneous fermentations, excellent grapes, and attentive winemaking are already contributing plenty of aroma in any case. A recent study (that actually concerns itself with the possibility of using non-Saccharomyces yeasts to alleviate some of the potentially harmful side-effects of fermenting at low temperatures) suggests that the microbial diversity that comes with spontaneous ferments is probably helping hold up aromatic diversity, and it’s not the only one (this excellent article on sauvignon blanc aromas points to advantages from yeast diversity, too).

In other words, I can’t help but wonder if fermenting at artificially-controlled cool temperatures is something we’re told we need to do because modern industrial practices strip aromas in other ways; that is, if we’re not compensating for less-than-ideal winemaking. Cooler fermentation might (or might not) make that gewürztraminer I enjoyed more aromatic, but it wasn’t wanting. The $15 mass-market version, on the other hand, probably needs all the help it can get.

Those oca, incidentally, threatened to steal the show from the wine. (I think the wine won, though: a bit off-dry, but well-balanced, with the sort of creamy richness I look for in a gewürztraminer and, of course, plenty of peach-lime zest aroma.) Should you catch some of these unusual almost-potato tubers in the market — or, like me, should the house you’ve rented have a patch of them resident in the back garden — here’s a suggestion. North American yams take well to the same treatment.

Tahini-miso oca for four (or two plus leftovers)

1 lb (450 gm) oca, washed and cut into approximately 1″ pieces if large

2 tbsp tahini

3 tbsp white or barley miso

2 tsp butter

~ 1 tbsp fresh thyme leaves, if available (or substitute 1 tsp dried thyme)

Heat about an inch of water in a medium-sized saucepan over moderate heat until steaming, then add the oca, cover, and steam over moderate heat for about 10-15 minutes or until tender all the way through when prodded with a fork. While they’re cooking, combine the miso and tahini in a small bowl. (The purpose of doing this, rather than just adding both to the pot individually, is to help the miso mix more easily into the oca. If you’re really interested in saving dishes you can just do the former, but you may end up with miso-lumps.) Drain any remaining cooking water from the pan. Add the tahini-miso mixture, the butter, and the thyme and toss gently until all of the tubers are coated in the sauce. Serve immediately.