New research: Wine allergies exist. You probably don’t have them.

A lot of people seem to think that they’re allergic to wine. Most probably aren’t. Our current best evidence on sulfites says that only people with severe asthma have any real cause to worry and, given the presence of sulfites in many other common foods – most dried fruit, many cured meats, salad bars – it’s something they surely know before ever meeting their first glass of wine. I’m one of a subset of people who react dramatically to biogenic amines, molecules produced by some yeast and bacteria that mimic human hormones and cause me to go hot and red in the face and sprout a bad headache after only a few sips of an affected wine (embarrassing when people think I’m tipsy after half a glass). Another subset (including many Asian people) honest-to-goodness doesn’t metabolize alcohol well, thanks to a genetically encoded difference in an important enzyme, and turns hot, red, and otherwise uncomfortable in response to any alcohol. None of these are actually allergies.

So, do wine allergies actually exist? Yes.

Back in 2012, a group of German epidemiologists sent out a survey asking random adult residents of Mainz whether they had experienced symptoms of “wine intolerance.” 7.2% of people who responded to the survey attested to some form of wine intolerance. I wrote about some problems with the study on Palate Press: the possibility that respondents might have confused “intolerance” symptoms with a hangover, the likelihood that the survey overestimated people with problems because they’re the most likely to respond (and three-quarters of people sent the survey didn’t respond), the power of suggestion. Still, the study begs the question. How many people really are allergic to wine?

The same group has followed up with more research aimed at answering that question. Of the 68 people marked as “wine intolerant” by the original survey, they convinced 19 to sit down, along with ten non-intolerant controls (mostly women), for a battery of allergy testing. In addition to the familiar skin prick test – inject a bit of potential allergen X under your skin to see if you come up red and swollen – they also used several blood tests all looking for the release of inflammatory molecules in response to wine and grape products, including riesling, pinot gris, pinot noir, and dornfelder wine. All of these tests measure reactions to grape proteins. These are true allergies, proteins that set off an immune response, not reactions to alcohol, biogenic amines, sulfites, or allergies to processing agents such as egg whites or milk proteins.

Seven of the 26 people prick-tested developed swelling in response to at least one of the wine or grape samples, four to wine and three just to grapes. 13 developed antibodies in response to grapes, but only nine of them had reported symptoms; the other four were in the asymptomatic control group. Only one person was wine allergy-positive in all four different types of tests.

The conclusion? People can be allergic to specific kinds of grapes, wines, or both, just as people can be allergic to citrus fruit, tomatoes, or olives. It’s probably not very common. This study was small, far too small to say anything about how common wine allergies are in Germany let alone amongst other ethnic groups. Knowing how to respond to discrepancies among the tests, and between the tests and people’s reported symptoms, is an issue, too. Writing up their results for publication, the researchers ignored it. But again, no matter what exactly is going on there, we’re back at the first conclusion. Grapes, and wine, seem to be like other foods as far as allergies go. You might well have a wine allergy, or an allergy to red or white wine, or to a specific variety. You probably don’t.

Empirical evidence: organic/biodynamic vit = more textured wines

A six-year comparison of organic, biodynamic, and “low-input” and “high-input” viticulture (three years of conversion, three of maintenance) recently came to fruition in South Australia, courtesy of researchers at the University of Adelaide. The full report is freely available here (and three cheers for research freely shared). It’s 73 pages long, but the conclusions are fairly simple. The most worthwhile among them: in blind trials, experienced wine professionals rated the organic and biodynamic wines more interesting than the conventional versions.

  • Soil health (nitrogen, phosphorus, organic carbon, microbe mass) was most strongly improved by compost, not by any particular management system. All four systems were tested with and without compost.
  • Compost had the single most dramatic positive effect on soil health, no matter the underlying management system.
  • Management system had no consistent effect on vine growth, berry weight, or berry composition.
  • Low-input, organic, and biodynamic alternatives yielded at 91%, 79%, and 70%, respectively, of the high-input condition.
  • Organic and biodynamic wines were more “textural, rich, vibrant, and spicy” than their conventional counterparts. (pH, TA, and color held constant; high-input wines were a bit higher in alcohol.)

Improved soil health with organic/biodynamic management has been demonstrated numerous times over, and so have the benefits of compost. This study was unusual in making compost a separate variable, showing that both organics/biodynamics and compost, separately, were beneficial. The upside here is the attitude, across the study, that conventional growers can benefit from organic techniques even without undertaking a full-on organic conversion.

The downside is that the “organic” and “biodynamic” management used in the comparison are weak compared with what many committed non-conventional growers undertake. How can you practice biodynamics without compost? “Biodynamic” here seems to have meant nothing more than adding the core preparations 500 and 501, a far, far cry from anything Demeter would certify as honest biodynamics. Even the organic system is pretty bare bones: weed control with mowing and cultivation instead of herbicides; no insecticides or pesticides other than copper. (The low-input condition pulled back on the insecticides and some of the pesticides.)

Talking about those lower yields, the researchers make an important point. Very little research has been done on organic or biodynamic cultivation methods. We could develop better techniques within those systems and preserve environment and fruit quality while improving yields. Many organic/biodynamic growers have surely worked out such techniques on a local scale, which leaves a role for scientists to listen to what they’re doing, identify why it works and how/whether it can be generalized more broadly. Some environmentally conscious wine people are happy to pour their big pharma money (or whatever it might be) into projects they believe in with no thought for financial return, but most are trying to support their families as well as their values. Sharing successful organic/biodynamic techniques — say, for weed management, which was the biggest issue in this study — developing them scientifically, and stamping them with a scientific seal of approval so that they’re not dismissed as just those quacky organic people, will help conventional growers improve their weed management tactics, too. Likely, too, with economic benefits you can appreciate even if you honestly don’t care about trashing the environment for short-term gains.

The researchers should have made another point about those yields. Are the high-input yields a reasonable benchmark? Should we buy short-term gains with long-term environmental and social damage? If your business isn’t “sustainable” without using chemical warfare to eke every last grape out of the earth, then perhaps you need to reconsider your business practices in other areas. It comes back to the old resurrecting dinosaurs argument. Just because we have the technology to do something doesn’t mean we should. The wine might even be more interesting.

 

Brett + bacteria = worse, or better

Microbiology has gotten a lot wrong studying yeast and bacteria. We’ve assumed, until quite recently, that if a microbe doesn’t grow in a dish it’s not there. And that a microbe is either on/live/growing or off/dead. And that we can study microbes in isolation — “pure culture” — away from other species in little sterile dishes and expect them to behave normally. In all fairness, microbiologists have sometimes seen these as a problems, but have mostly just gone on this way, writing books about what we think we know.

DNA detection and sequencing technology is showing just how many bugs don’t grow in dishes — “high throughput” technology can document (theoretically) all of the species in a drop of [insert favorite liquid here]. That’s pretty routine these days. And we’re slowly beginning to study how mixtures of microbes — you know, the way they live in the wild — behave in the lab. Wine was a bit ahead of the curve here: microbial enologists have been studying the goings-on of spontaneous and mixed fermentations since the late 1980’s.*

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There’s fat in your wine, but the fatty acids are the issue

Oil and water don’t mix (unless you add egg, but then you’ve got an emulsion…and mayonnaise). Wine is essentially water plus alcohol, which doesn’t mix well with oil, either. Since there’s no oil slick layer floating on top of your glass of wine the way fat drops glisten on top of a bowl of ramen, you’ve probably assumed that the wine is fat-free. And if you Google “is there fat in wine?” about 102,000,000 results will tell you that you’re right.

Which is wrong, sort of. Wine does, strictly speaking, include very small amounts of fat. New and improved chemical analyses of New Zealand sauvignon blancs have identified that they at least 25 different kinds of triacylglycerides — the chemical reference for your standard fat molecule: three fatty acids (tri-acyl) bound to a glycerol molecule (glyceride). That’s in addition to an assortment of other fat relatives such as free fatty acids and some waxes.

It’s actually the free fatty acids that are most important here. (Those fats are there in such minuscule quantities that even the jumpiest health journalist can’t pretend there’s anything to jump about there.) They’re present in milligram per liter quantities (so we’re talking less than the amount of sugar found even in truly dry wines) which is enough to make a significant sensory impact on wine indirectly. 

Yeast need lots of free fatty acids to grow well; they’re a major raw ingredient for new cell walls. With plenty of oxygen they can make their own; without oxygen, that particular yeast production line shuts down. Fermenting wine is a mostly anaerobic job for yeast: they get a little oxygen exposure at the top of the vat, a little if the wine is vigorously mixed to keep the skins submerged, but mostly need to rely on the fatty acids initially contained in the grape juice to tide them over. If that source fails, a long and very complicated chain of yeast stress response events kick in, ultimately ending in stuck fermentations, icky aromas, or both. In short, the amount and kind of fatty acids in particular and lipids in general affects wine aroma.

That’s not a wholly unheard-of problem. Overly enthusiastic efforts to clarify white juice before fermentation can pull fatty acids out, too, to the yeast’s detriment. But, ironically, the more common issue is too much of the wrong kind of fatty acid after the yeast have been at it awhile. Lacking the ability to synthesize cell wall components they really need, too much of cell wall molecules they can make (decanoic and octanoic acids) accumulate with toxic consequences. The effect fatty acids have on yeast is a bit like the effect fat has on humans: too much of the wrong kind kills us after awhile, but not enough of the right kind can cause serious problems, too.

But there’s a different and possibly more interesting point to be made here. Lipids originally present in the grape juice affect yeast metabolism, which affects wine aroma, which gives us new places to intervene to make alterations. Adding lipids to South Australian chardonnay boosted production of aromatic molecules: esters, aldehydes, higher alcohols, and volatile acids. The authors of that sauv blanc study speculate that adding specific lipids might be a way to create new, different styles of that so very identifiably aromatic wine.

This information is splendid in two ways. First, it tells us more about that complex and ill-described business of how winemaking works. Second, it may be a way to experiment with new wines. But, third, it could open up one more avenue for adding stuff to make wine fit a particular sensory profile, which we might more generally call “manipulation” and to which many of us* are generally opposed but which fuels the contemporary commercial wine-as-supermarket-commodity industry and supplies inexpensive reds and whites to fit market niche-targeted profiles specifically designed for the glasses of middle-class suburban mothers between 31 and 40 or single 22-29 condo dwellers who prefer to drink wine before dinner with friends on Thursday and watch Orange is the New Black. All wine is manipulated, all wine contains fat, but what that means for any individual case is a different question.

 

 

*Assuming, perhaps unfairly, that “us” is mostly comprised of people who prefer to drink and/or help produce unique and expressive wines that rely more for direction on local traditions, personal philosophy, and vintage conditions than Nielsen numbers.

 

High alcohol wines dial down your brain (but does it matter?)

My April piece for Palate Press pokes at the question, “how can we really tell what we’re tasting” by removing as much of the subjective mess around language as we can and going straight to the brain. Using functional magnetic resonance imaging — stop-motion shots of your brain in real time as you perform some kind of task, like tasting wine — we can look for differences in what parts of your brain are active when you’re sipping on wine A versus wine B and infer something about what effect they really have on you. Variations on the theme let us ask all manner of interesting questions. Make wine A and B the same, but tell tasters that one’s expensive and one’s cheap. Brain reward centers will light up more in response to the “expensive” wine. Or keep the wines the same and change the people. Trained sommeliers think demonstrably more and more analytically about wine tasting than casual sippers. Or try to pair up wines to be as similar as possible save for their alcohol level and ask whether tasters prefer the higher or lower alcohol versions.

Okay. The last one is  a stretch. Scientists have done it and shown that higher alcohol wines provoke less brain activation than their lower alcohol counterparts. That’s interesting, particularly because researchers expected the opposite. Instead of more intense wine provoking more intense sensation, it seemed that tasters had to work a bit harder to pay more attention to the subtle nuances in the less hit-you-over-the-head reds.

Okay. I suspect knowing this doesn’t change much for you if you’re a winemaker, but perhaps if you’re running complex formal tastings — either for sensory science experiments or to train sommeliers or diploma students — you now have more evidence to back using lower-alcohol wines to improve students’/subjects’ learning and focus.

But, can we say anything at all about whether tasters prefer the lower- or the higher-alcohol versions? Here’s where they’re stretching. Specific types of brain activation tell us things about pleasure, no doubt: we’ve identified “reward centers” and “pleasure centers” and we can even visualize people drawing associations with memory and emotions (perhaps you’ve made the acquaintance of your amygdala?). But to say that, because higher alcohol wines “dial down” the brain, relatively speaking, tells us nothing about what you should drink when you’re trying to maximize the pleasure of that evening out at the restaurant you’ve been anticipating for weeks.

Far too many other factors come to bear upon wine preference for us to imagine that these study results say much (if anything) about it. My somewhat embarrassing preference for light-bodied Willamette Valley pinot noir is a good example. I appreciate and enjoy virtually everything (just because I’ve never tasted a white zin I could enjoy doesn’t mean it couldn’t exist), but I have a soft spot for raspberry and pine and ocean spray-scented, fine-boned, earth and mushroom-framed pinot. Like the ones I grew up on as a kid scampering around a big front yard abutting a vineyard on Cooper Mountain. I have so many pleasant memories associated with that style of wine, long conversations with my father, warm evening light spreading across the great big round dining room table he made, and mud squishing through my toes while I picked the green beans that I’m going to prefer it, even if it turns out that they require less cognitive attention, even if every critic tells me that they’re poorly made, even if I learn to assess quality by other criteria.

Duh. I haven’t said anything earth-shattering. And, in one way, the difference between a marketing study and a neuroscience one is whether that gestalt gets captured in overall “behavior” or whether one factor is isolated and analysed. The neuroscience is still useful for describing how wine works (something marketing studies rarely do well, to be honest). But it does squat for speaking to complex behaviors made up of scores of these bitty considerations which we need to remember aren’t anywhere near as binary and are a whole lot messier than simple science like this fMRI study makes them seem. So let this be a counterpart to all of the enthusiastically reactionary science journalism that responds to press releases about people drinking wine in giant magnetic tubes by shouting “Science discovers high-alcohol wines aren’t really as good after all!” from their collective rooftop. Nope. We’re not there yet.

One more reason why wine is good for you, and not just the red stuff

When it comes to health benefits, red wine tends to get most of the credit.

Cardiovascular benefits have been ascribed to alcohol itself (find a reasonably readable and full-text review here, courtesy of the Journal of the American College of Cardiology). But, of late (as in, say, the past decade), resveratrol has attracted the most attention; as a potent antioxidant, it truncates the chain of events involved in endothelial plaque formation (“hardening of the arteries”). Resveratrol is much more concentrated in red wine than in white. But resveratrol is a polyphenol, one of many. And polyphenols in general, and both red and white wine, have circulatory system benefits in lab studies we can ascribe to other causes.

For instance, NO, which is to say nitric oxide. Polyphenols encourage artery-lining cells to produce more NO. We know NO both as laughing gas and as a potent (if short-lived) vasodilator. NO tells the artery muscular to relax, which increases vessel diameter and lowers blood pressure. Arteries that no longer relax properly are a feature of many cardiovascular diseases and part of the cascade of interrelated faults that progressively damage both the heart and organs like the kidneys and eyes that suffer damage from blood pressure that’s consistently too high. NO also helps makes platelets less sticky with the effect of gently working against that damaging plaque formation.

Antioxidants, including polyphenols, increase NO levels indirectly by countering oxidative molecules that can rapidly destroy NO in the bloodstream. Polyphenols also stimulate NO production directly, and arteries benefit by learning to relax and suffering clogs less readily.

A paper just out in PLOSOne (always and ever open access) convincingly adds to evidence that caffeic acid, a polyphenol in which white wines are particularly rich, increases arterial lining NO production. The research team demonstrated that caffeic acid increases NO, but also that it improves arterial cell function and slows kidney disease damage in mice. Translating caffeic acid-dosed mice to white wine-dosed humans is still a leap we’ve not yet made, but it’s a likely one. Doses mice received were along the lines of what a moderately-drinking wine lover might ingest, and these sorts of mouse experiments have worked well to model human arterial disease in the past.

In short, there’s a good argument to be made that white wine is good for your heart. As good as red? That’s going a step too far, and not least of all because individual wines vary so much in their concentrations of resveratrol and caffeic acid and total polyphenols that we’d need to compare individual wines rather than try to stereotype by color. But the next time someone tries to talk you out of a glass of Chablis or riesling in favor of the red option for the sake of your health, don’t let them. You know more than they do.

In other news: three useful-if-not-groundbreaking reviews arose in recent days, on biotech uses for winery waste products, causes of and solutions for protein hazes, and polyphenols found in oak. Details are here.

For organic wine, sharing information isn’t always better

Premise one: Organic labeling laws are complicated, non-intuitive, vary from country to country, and are disputed more or less everywhere.

Premise two: When Joni Mitchell sings “give me spots on my apples, but leave me the birds and the bees,” not everyone agrees with her, and some people think the spotty apples aren’t going to be very good.*

Warrant: Because consumers are confused by what “organic” means and because they associate “organic” with forlorn and spotty produce from the non-local and meagre selection at the grocery store, some may think that wine labeled “organic” is sub-par.

The most useful part of a recently published study on “eco-labeling” may not be the data, but the way the authors explain why it’s worth talking about in the first place. They explain “eco-labeling” as being about alleviating information asymmetry between producers and consumers, which is another way of saying that labelling is about trying to share what we know. And with wine, knowledge often goes along with enthusiasm.

Organic wine marketing ends up singing the same song I hear so often from folk in science communication: I know that my science is phenomenally exciting/important; I want to tell everyone else about it; why can’t I get everyone else as excited as I am? All of that excitement and deep caring makes it easy to fall into the solipsistic trap of telling everyone else all of the great details about what I do so that they can know how great it is, too.

Delmas and Lessem’s is only the most recent in a line of studies saying that more sharing isn’t always better. In an online simulated buying exercise, they asked potential wine buyers to choose which bottle they’d prefer to buy amongst a few invented-but-likely California cabernet sauvignons** with labels indicating “organic wine,” “made with organic grapes,” or none of the above. The wines were, in different versions of the exercise, from Napa or from Lodi and priced at $8, $15, $22, or $29.*** Their survey respondents were mostly Californian and younger, better educated, and a good deal better off than national averages, but so are a lot of potential wine consumers and what they found is consistent with previous studies.

A third of their respondents buy organic products on at least half of their shopping trips and 20% said they belonged to some kind of pro-environmental organization, and these folk were more inclined to prefer the organic-labeled wines. But better educated and wealthier respondents were more inclined to choose wines without organic designations. Lower-priced Lodi wines with organic on the label faired better than higher-priced “organic” or “made with organic grapes” Napa wines.

All of this is to say that this study is one more in a pile saying that consumers — even well-heeled Whole Foods-shopping eco-conscious Californian consumers — probably still think organic wine is wan and spotty. If you’re trying to sell premium wine and your environmental conscious leads you down the organic route, more information isn’t necessarily better.

The problem with marketing studies is that despite all their schmancy formulae and big tables full of numbers and tests for statistical significance, they don’t tell us much. Did people who didn’t prefer organic wines (especially the regular organics buyers) avoid them because of past experiences with icky low-quality bottles? Because they’ve heard stories about other people’s experiences with icky low-quality bottles? Because they know the details of the sulfite controversy, or just assume that organic wine isn’t as good, or because they think organic wines are overpriced or have cooties? If we can get those marketing folk to spend some of their time talking to people instead of just crunching numbers, organic supporters will have a better song to sing when we come back to those labeling disputes.

 

*Writes with sadness the person who’s been happily munching spotty apples from a nearby feral apple tree  that easily beat out any of the overhybridized, artificially sweet specimens from the grocery store or even the farmers’ market.

**Amusingly enough, their likely-sounding fictitious wine brands were common French surnames. Because, sensibly enough, consumers expect Californian wines to look and sound French. Really?

***Though how you simulate a believable $8 Napa cab, organic or not, is beyond me. Have I mentioned my qualms with marketing studies? This study makes a lot of assumptions that I find unwarranted, but none that substantially affect the core findings of their survey.

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.

If you could learn which yeasts actually ferment your natural fermentation, would you?

The Australian Wine Research Institute (AWRI) has launched a new winery service. Winemakers can now submit samples from natural/wild/native/non-inoculated ferments (or, conceivably, from an inoculated one if they wanted to) and, courtesy of “next-generation DNA sequencing*,” receive a profile of the yeast species present along with approximate percentages. An additional step can give them more specific strain information, and the AWRI can also isolate, freeze down, and store the main yeasts from your sample as “insurance” if you need them in future vintages.

This sounds like marvelous geekery. Winemakers who don’t inoculate probably wonder about what’s going on in there at least occasionally. What I’m unsure of is whether this yeast profile is a useful management tool beyond a fun way to satisfy your curiosity (or give even more detailed information to very well-heeled consumers). I imagine the following scenarios:

Good natural ferment — You like what’s happening with your uninoculated wine. You’re going to keep making it even if you learn that some generally undesirable bug has part of the action because you know you like the results. Maybe having a yeast profile sets you a benchmark so that if the ferment stops working in some future vintage you can send in a sample for comparison and see if the microbial blend changed, but how does that information then change what you do?

Bad natural ferment – You’ve tried not inoculating a wine and it isn’t working for you for whatever reason. You send in a sample from one that didn’t work (too slow, undesirable flavors, or didn’t finish fermentation). Maybe you’ll learn that some toxic bug is out-competing the yeasts you need to grow, or you’ll identify the source of that high volatile acidity you’ve been combatting. What then? The natural ferment still doesn’t work. Can you tweak pH or how much sulfur dioxide you use or your oxygen management to encourage more favorable microbes against the enemy? I don’t know how likely someone is to successfully adjust or amend a natural ferment to work better at that level — from the perspective of philosophy as well as how likely it is to work — but if you’re going to try these strategies, you’ll likely know to try them without knowing which yeast species are involved.

Planning a natural ferment – Maybe you run a test natural ferment to see whether you like what it does, and you want to “double-check” that it’s okay. The primary information you need stays the same: does it ferment to dryness? does it move fast enough to satisfy your economic needs and peace of mind? does it taste good? These will remain the primary drivers of your decision to move ahead or not, independent of what you learn from that yeast profile.

This service can help answer that perennial question of whether the yeasts in your “wild” ferment are really wild or just commercial yeast strains that have colonized your winery, and to some extent (especially if you go down to that extra strain level sequencing) the degree to which your ferment is different from some other winery’s. But the question — the AU $275 question for running a single sample, or AU $792 for the recommended panel of three samples per ferment — is this: will the extra information change what you do?

Nevertheless, forward-thinking actionability isn’t everything. Even if a winery never tries to replicate a previous successful wine by inoculating with its bespoke mix of strains banked through the system (that seems unlikely to succeed simply given the enormous variability in other parameters affecting wine quality directly and indirectly via influencing yeast growth), a retrospective look at yeast mixes in multiple vintages of the same natural ferment could be interesting. Did a change in viticultural management practices, or source of grapes, or fermenting conditions correlate with a clear change in microbial populations? That prospect makes me hope for two things. First, that a winery (or a dozen or two) will use this as a tool for looking back at the path they’ve taken and not just down at where they’re standing. Second, that when they do, they’ll share.

 

*Next-generation DNA sequencing (this introduction from Nature is dated and technical, but it’s also open-access; the article on Wikipedia is also quite good) is a collection of methods so called because they rely on new strategies for sequencing DNA — not just tweaks of the old traditional way, but really new ways of solving the problem — that let us do things differently, faster, and more efficiently. The most important things to know about next-generation sequencing are that, 1) it’s not a method, but a general term for a whole bunch of methods; 2) the idea has been around since 2008, which doesn’t mean that any of those methods can’t be cutting edge but which does mean that they’ve “trickled down” to the general market by now; and 3) they allow for pulling many sequences from many different organisms out of a single small sample. Old sequencing methods required a relatively large sample of (preferably) a single pure target sequence or else the signals would get so jumbled up that the whole instrument read-out would just look like soup (as I recall well from my first sequencing experiments as an undergrad in 2002-3). Now, we can sequence even single stretches of DNA, and even many different single stretches all hanging out in the same sample from some real-life microbe-rich setting: soil, seawater, or an active ferment. And we can do it quickly and inexpensively enough, now, to offer it as a commercial service. Remember those predictions about what genomics would bring us back around 2000, when sequencing genomes really hit the news? We’re getting there.

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.