Good data (and good conclusions) on (not much) arsenic in CA wines

Short: A new article in the American Journal of Enology and Viticulture publishes data showing that California wines contain honest-to-goodness insignificant amounts of arsenic. Even if you can’t call the authors completely disinterested, they’ve published their data openly in an excellent scientific journal (and that’s a lot better than you can say for the arsenic fearmongers).


At the risk of bringing up what must surely be everyone’s least favorite wine story from 2015, I’m writing once again about arsenic in wine. I hope you’ll agree with me that, given the reason, it’s justified. A group of reasonably trustworthy researchers has published a scholarly research article demonstrating that California wines don’t have an arsenic problem, and while their work won’t put the arsenic-wine baby to bed once and for all, it goes a long way in the right direction.

My denigration of the perpetrators a year before the scandal broke is here, and my response to the scandal itself is here.

Two problems have lain at the bottom of all of the talk about arsenic in wine. One is that no one – not the US government, not the World Health Organization, and not expert toxicologists talking amongst themselves in the peer-reviewed toxicology literature – is sure how much arsenic is too much arsenic. The other is that the people talking about arsenic in wine haven’t been transparent with their data. This article doesn’t help with the first problem, but it does help with the second.

In short, two independent wine testing labs ran arsenic stats for 28 wines named in the arsenic-related lawsuit brought against California wineries, plus 73 other California wines bought essentially at random* from stores in Pennsylvania and New York. The results:

Wine category                               Mean arsenic concentration                      Standard deviation

Reds                                                6.75 µg/L**                                                    7.33 µg/L

Whites                                           10.9 µg/L                                                         11.0 µg/L

Rosés                                             27.2 µg/L                                                        16.9 µg/L

The first and most important thing to observe about these numbers is that they’re all dramatically lower than the 100 µg/L guideline Health Canada has set for wine and even more dramatically lower than the 200 µg/L the International Organization of Vine and Wine (OIV) has set for its members (of which the United States is not one, but which includes nearly every other significant winemaking country around the globe). (The United States hasn’t regulated arsenic in wine.) Even the wine with the highest concentration of arsenic in this study clocked in at 68.4 µg/L. Yes. Some of these numbers are higher than the 10 µg/L the US Environmental Protection Agency allows in drinking water. But do you drink wine the same way you drink drinking water? Compare wine to food, not to water.

The second thing to note is that, generally speaking, cheaper wines had higher arsenic concentrations. That’s both interesting and not unexpected. (Higher concentrations in rosés and whites than reds, incidentally, isn’t a factor of price. The white >> red phenomenon has been observed in other studies and is assumed to have something to do with processing, though we’re unsure what.)

The third thing to know is that the wines cited in the lawsuit had higher arsenic concentrations (25.6 µg/L) than the random wines (7.42 µg/L), but even the lawsuit-associated wines were still dramatically lower than the 100 µg/L guideline. The wines in the lawsuit were cheaper, generally speaking, than the average wines.

And the fourth thing to note, once again, is that you don’t need to be worried about arsenic poisoning from wine. These researchers did something I think is silly and calculated “average daily” arsenic exposure from average wine consumption data rather than calculating exposure for a heavy-imbiber. To generalize just a bit from their data, the average American drinking two five-ounce glasses of Californian wine a week, every week, will get no more than 10% of the arsenic in her diet from wine, even if she’s drinking the cheap stuff. Arsenic is naturally present in the environment. It’s in water, rice, meat, beer, and bread. If you smoke, you’re getting arsenic in tobacco.

I’m not willing to call this research “unbiased.” Research is never unbiased; scientists can’t escape having a point of view any more than you or I, and it colors the scientific process from the questions they ask to the methods they choose, the way they read their instruments, and the conclusions they draw even if they’re trying in all earnestness to be objective. The labs behind this paper have also run tests and provided evidence for the wine industry in the past, and it’s presumably in the authors’ best interest to conclude in the wine industry’s favor. For that matter, it’s also in the best interest of the publishers of the journal, the American Society for Enology and Viticulture, to side with California’s wineries. All of that said, everyone’s long-term reputations here are best-served by being fair and transparent and there’s every good reason to think that they’re doing just that. And that’s a lot more than can be said for the arsenic fearmongers BeverageGrades.

*The researchers used a “convenience sample,” which in this case means that instead of trying to devise some strategy for obtaining a “representative” sample, they used what they could find. Convenience samples are sometimes a real problem in research (when a psychologist uses the freshmen in his psych 101 class to represent the American public, for example), but here this strategy makes a lot of sense: these are wines you’re going to commonly find as a consumer.

**µg/L = micrograms of arsenic per liter of wine

Whey proteins for reducing astringency: If it works for tea…

Important note: The following story should NOT lead you to conclude that you need to stop drinking wine if you generally avoid dairy. Please see the comments at the bottom of this post, this post on wine allergies (and why you probably don’t have them), and this post on gluten in wine.

Short: The main protein in whey, a voluminous byproduct of cheesemaking, might be a good (and cheap) fining agent for reducing astringency in red wine, but it’s going to need a lot more testing, and I’m (very) suspicious.


Many people* add milk to black tea because it softens the harsh edges of what is so often an unfortunate cup of broken orange pekoe. The combination works because a milk protein, β-lactoglobulin, binds tannins. This was news a few years back because adding milk reduces astringency, but not nutrition value (unless you’re filtering large macromolecular complexes out of your milky tea, and I can’t imagine you are). Whey protein-bound tannins won’t bind to your salivary proteins to dry out your mouth, but still work as antioxidants in your body.

Adding β-lactoglobulin from whey protein might for essentially the same reasons be useful to decrease the astringency of red wine. Casein, another milk-derived protein, is routinely used for wine fining. The benefit of making the switch is cost. Casein ends up in cheese. β-lactoglobulin ends up in the whey left over after making cheese. Ergo, the cheese-eating world has more β-lactoglobulin sitting around than casein, body-builders’ post-workout protein shakes and the occasional bottled whey beverage notwithstanding.

This is one of those so obvious and sensible-sounding ideas that I’d be inclined to think: surely someone’s already tried this and found that it doesn’t work or everyone would be doing it already. Still, a quick search of the scholarly literature suggests that no one has, publicly, though this study from 2007 found that β-lactoglobulin binds well to resveratrol.**

The chemists behind this just-published study found that β-lactoglobulin reduced astringency about as well as gelatin, gram for gram, at least for the random cheap French merlot they tested. Even better, β-lactoglobulin worked about as well as a combination of β-lactoglobulin and casein.

If you’re waiting for the catch(es), here they are:

  • β-lactoglobulin shouldn’t work as well as gelatin on the basis of established knowledge about tannin-protein interactions. Tannins bind best to big, loosely folded proteins with lots of an amino acid called proline. Tannins bind less well to small, balled-up proteins. Gelatin (and some major salivary proteins, coincidentally) are loosely folded and proline rich. β-lactoglobulin is small and balled up. The authors make a gesture toward figuring out why β-lactoglobulin still works by quantifying the concentration of total protein-precipitable tannins and a few specific, important tannin molecules in the wines before and after treatment with gelatin, β-lactoglobulin, or the β-lactoglobulin-casein combination. Those tests confirmed that β-lactoglobulin is binding tannin molecules, but also that they’re binding weakly.
  • This weak binding seems to involve groups of tannin molecules strung together. β-lactoglobulin doesn’t do a good job of binding to individual tannin units (monomers) hanging out in the wine on their own.
  • These authors only tested whey protein with one red wine (the random French merlot), and only measured astringency by chemical approximations, not with real swirling and spitting tasters. So I’m suspicious. Surely, the idea of using whey protein for wine fining has occurred to at least one food processing house or winemaking supply company with the resources to test the theory out on their own, on many different wines, with their in-house sensory panels doing the tasting. If it worked, whey protein would be on the market. If it didn’t, they might well not broadcast the news. And – forgive me this, because excellent research can come from unlikely places – the authors are from the University of Reading in the UK and the National University of Rosario in Argentina, neither of which is a hot bed of groundbreaking wine research. That’s not to say the researchers aren’t good, but it is to say that they might not have ideal access to the accumulated wisdom of the field.

An interesting idea. Unlikely to be the next wine chemistry success story, but an interesting idea.


*I add milk to black tea on rainy days because the aroma evokes England and memories of a childhood I never actually had of drippy days shut up inside with endless tea and books in a British country house. I can tell you this because it has rained here every day for more than a week.

**I think that at least the general idea that β-lactoglobulin binds to wine tannins might be buried in this 2011 masters thesis conducted at Massey University in New Zealand, but I’ll be honest: I didn’t have the patience to read the whole thing carefully enough to find out.

Playing the “what’s that smell” game with aged red Bordeaux

One of wine chemistry’s best parlor tricks is the “what’s that smell” game. Why does your wine smell like raspberries, or turpentine, or mint? If there’s not yet a chemical explanation for how it got there, we can often at least point to a molecule. And as various plays on molecular gastronomy have made clear, pointing to the molecule can be a lot of fun. We can ask where else that molecule pops up and devise creative food-wine combinations, or just marvel at the envirochemical systems that make compounds produced by South African trees pop up in aged red Bordeaux.

Speaking of South African trees and aged red Bordeaux, recent wine chemistry research has identified a molecule best known from the former as the explanation for minty aromas in the latter. A group of (no surprise) Bordeaux wine chemists have concluded that the classic minty-ness some red Bordeaux acquire* can be attached to piperitone, a molecule previously undiscovered in wine but, the European Bioinformatics Institute tells me, is commonly extracted from South African eucalyptus trees.

Along the way, the authors make a second and perhaps more interesting point about how chemists go about pairing up molecules and aromas. A typical method involves gas chromatography-olfactometry: the gas chromatograph separates out the components in a (vaporized) sample, and the olfactometer lets you systematically sniff the components that come out of the chromatograph. The excellent thing about this method is that it lets an experimenter identify the “odor-active” components of a sample. The downside is that you’re smelling and studying each of those components individually rather than investigating how they interact or what difference they make to a wine’s total aroma. Even if the conventional tasting note gives individual aromas as though the OWP** is smelling down a list, smelling is more complex than that. The wine-sniffing nose receives a whole pile of odor-active molecules at once, the brain processes them together, and then our memory and language processing functions arrive at descriptors that probably aren’t one-to-one matches for the molecules that came in at the front.*** At least in theory, a molecule may smell minty without contributing to how we perceive mint in a wine, or vice-versa.

An alternative this article touts is “aromatic reconstitution:” a complex sample (vaporized wine, for example) is separated out into odor-active “fractions” using that gas chromatograph, and the fractions are recombined in their original proportions but with one missing. Meanwhile, other wines naturally lacking the smell-of-interest are spiked with the most interesting odor-active fractions. The recombinations and spiked samples are smelled, and results are tabulated for what smells appear or disappear in association with what fractions. Researchers can then go back to the fractions that matter the most to the smell-of-interest and work out what the heck, molecularly speaking, they’re dealing with. Much to their credit, in this study local Bordeaux wine professionals were pulled in to do the smelling.

All of that (and a lot more, in this very thorough study) let the researchers say that piperitone contributes to the minty aroma of aged red Bordeaux, a much stronger conclusion than saying that piperitone is found in aged red Bordeaux and piperitone smells like mint without directly connecting the two. The piperitone-mint link might have useful consequences of some kind for people with wine aging problems or chefs creating gently eucalyptus-scented lamb roasts, but it’s also one more step toward working out the moving parts of both smell and wine aging. And eventually, that’s going to be more than a parlor trick.

*Including, in this study, a 1998 Pomerol. I mean, it probably wasn’t Petrus, but this still sounds like the researchers enjoyed themselves.

**Obnoxious Wine Professional

***How the brain processes smell is a good deal more complex than I’m making it out to be here, and neuro-sensory-scientists are still working out a lot of the details. Modern science tends to be pretty good at teasing out how representational processes work – how we see, for example – but seems to make a lot less progress with affective processes involving emotion and non-linear, extra-logical processes.