Analytical chemistry says that Scotch whiskys really are different

Short: The Scotch industry has new scientific evidence that different single malts and blended Scotch whiskys are complex and distinctly different from one another. (Unlike, the suggestion might be, some mass-produced American “craft” whiskeys.)

Long: You can learn a lot about a field by its acronyms. Acronyms arise for awkward word-strings that a certain flavor of professional uses often but everyone else uses infrequently enough for English not to have a better and less cumbersome word for whateveritis. Winemakers talk about MOG: Material Other than Grapes.* MOG is interesting because winemakers are generally trying to get rid of it. Mass spectrometry experts talk about NOM: Natural Organic Material. Wine is a NOM. NOM is interesting because it’s replete with myriad compounds at miniscule concentrations and therefore helps spectrometer-ers figure out how good their techniques are. Mass spec is interesting to NOM-lovers because its a good way to learn about the composition of the NOM. And who are NOM-lovers? You are. Wine is a NOM. So is whisky.

A batch of analytical chemists from Scotland has just published a new article (open-access) in the Journal of the American Society of Mass Spectrometry (no, I didn’t know that existed, either) applying a particularly sensitive and wide-seeking version of mass spectrometry (more detail on what that means below**) to quantify the complexity of single malt and blended Scotch. Across 85 different commercial whiskies, they found 4271 unique molecular fingerprints – not precisely the same as identifying 4271 unique molecules because of the kind of data mass spec generates, but definitely evidence that whiskies are very, very complex mixtures. Only 407 of those probably-molecules were common to every whisky, and only about a thousand were common to 75% of the samples. In short, whiskys are highly variable, and perhaps even more complex than you’ve been imagining.

That result should please the SWRI – an acronym you’ll recognize if you’re in the spirits trade and that I should otherwise explain stands for the Scotch Whisky Research Institute – who provided funding for the study. A cadre of American “craft” whiskeys have been attacked from many quarters (including NPR and Serious Eats) for being remarkably similar across brands and price points and, not unrelatedly, for originating in the same industrial production facility in Indiana. Funding analytical chemists in Edinburgh looks like a Scottish move to assert that Scotch is the real deal, and maybe that consumers’ money is well-spent trying honest-to-goodness different brands.

That implication brings us back to the NOM. For the chemists, the choice of NOM isn’t precisely inconsequential – I know that the lead author on this paper is a NOM-lover himself, and they obviously wouldn’t have won funding from the whisky industry if the lab was studying, say, latex wall paint. But this study is published in a journal of mass spectrometry, and at least a large fraction of the point here is about demonstrating the prowess of their hardware and analytical methods. And that point has to do with the kind of data this study provides. We know that whiskys contain a lot of unique molecules, and we know that different whiskys contain lots of different molecules. What we don’t know is anything about how or whether those molecular differences translate to sensory differences. But since the SWRI is interested in Scotch, not just in NOMs, I suspect that we may be seeing that sensory study soon.

 

* Material other than grapes that ends up in collection bins with grapes, not all non-grape matter everywhere; winemakers might get accused of singlemindedness, but they’re not that bad.

**Mass spectrometry, broadly speaking, is a method to identify chemicals by their mass which, given that every kind of atom (think the periodic table) has a unique mass and molecules are defined by their atomic composition (and how those atoms are arranged, which makes life more complicated), makes mass spec something approaching a molecular fingerprint. Mass spectrometry, narrowly speaking, is any one of many, many different versions of that general principle, all of which have their own acronyms. These folk sent their 85 samples of fine Scotch through ESI-FT-ICR MS, which means electrospray ionization-Fourier transform ion cyclotron resonance mass spectrometry, which means that the scientists didn’t have to decide in advance which compounds they wanted to look for.

Don’t worry about mercury in whisky (but maybe worry about England?)

Mercury in single malt whisky is something about which you should never be concerned. Seriously, don’t worry about it. A recent study tells us that even the most highly contaminated bottles are more than 600 times lower than the World Health Organization’s current guideline for acceptable levels of mercury in drinking water. That’s for something you drink by the tablespoonful versus something you drink by quarts or liters. There is nothing to worry about here.*

So why bother talking about it, or measuring it in the first place? The authors behind that study were following up on a medium-sized hullaballoo in the mid-1990’s over relatively high concentrations of polycyclic aromatic hydrocarbons (PAHs) in single-malt. If that acronym looks familiar, it’s likely because PAH’s are the reason for the shadow cast over our grilling habits and, if I die of cancer, a probable place to point the finger.** PAHs are carcinogens formed by incomplete combustion that gives off smoke; in other words, PAHs are a minor-but-maybe-significant component of that marvelously flavorful char that accumulates on the outside of your barbecue, part of what makes smoked salmon such a very worthwhile thing, and one of the many reasons why cigarettes are a really nasty habit. It’s logical to suspect that they might be part of smoky single malts, too, which a group of researchers did strongly enough to bother studying it.

Chemistry confirmed the logic: moderate concentrations of carcinogenic PAHs showed up in the Scotch. But it also found something else. Single malts were worse off than American bourbons or Irish whiskies and even than blended Scotch. Worse yet, from my perspective, they found the highest concentrations in Laphroig and Oban, two of my favorites. Drinking whisky is associated with increased risk of colorectal, esophageal, and mouth cancer in the sorts of studies that measure such thing, though the researchers said that the concentrations of PAHs they found weren’t high enough to explain those risks.

So why the leap to mercury? Whiskies from southern Scotland turned up with higher PAHs than whiskies from northern Scotland. It’s well known that the south and west of Scotland is subject to more pollution than the north and east; it’s changing, but coal- and oil-burning proportionally overload the southwest with various airborne unpleasantries that end up migrating to soil and water and, evidently, to whisky. But maybe those Islay whiskies weren’t high in PAHs because of their proximity to the more densely populated and polluted parts of the country (and England). PAHs could just as easily come from those peat-smoked malts or the oak barrels used for aging.

If whisky’s carcinogens are a function of environmental pollutants, then concentrations of other environmental pollutants should follow the same south-north gradient pattern. And so we have the mercury study. Mercury levels in every whisky they tested were far too low to cause concern, but they nevertheless followed that same pattern: higher in the south, lower in the north.

This is a good thing, even for me and the rest of the hyper-peated club. Environmental pollutants from coal and oil combustion have declined massively, more than 90% since 1970, and continue to fall. Off-the-shelf whiskies the chemists tested were at least 9 years old, reflecting the environmental conditions of a decade or so ago. Tracing carcinogens to those conditions rather than to part of the whisky-making process itself means that it’s becoming less hazardous all the time. Or, at least, less hazardous in this one respect. Anything as delicious, expensive, and high-octane as a good single malt is always going to be at least a little dangerous.

 

*In light of recent events, I feel the need to make myself perfectly clear on this point.

**My diet is pretty ridiculously high in fruits, vegetables, whole-grains and all of those things we’re told should protect us in times of cancerous trouble, but I have an abiding weakness for smoked and charred foods. And I spend a lot of time with candles and incense, and I’m Catholic, which evidently doesn’t help.

***Which warrants quoting in full a letter to the editor sent to the Lancet following up on the PAH study:

Sir

As a member of the Scottish Malt Whisky Society, I found Kleinjans’ (Dec 21/28, p 1731)1 report of polycyclic aromatic hydrocarbons in whiskies of interest, but have one question. Since the authors used only 200 mL of each of the 18 whiskies studied, what did they do with the remainder? I hope that they had a very merry Christmas.