Tracing down tobacco aromas in aged brandies

I’ve become so accustomed to fermented beverages having flavors completely unrelated to their starting ingredients that I all too easily forget that there’s anything strange about it. And then I introduce someone to wine tasting for the first time and find myself having to explain that, yes, the wine tastes like cherries and no, they don’t put cherries in the wine to get it to taste that way. (But also sometimes that, yes, the wine tastes like oak, and yes, they do put oak in the wine, or wine in the oak, to make that happen.)

Wine and aged brandies, like Cognac, sometimes taste like tobacco. No one adds tobacco to them.* What happens instead is an example of what you could liken to chemical convergent evolution. Brandies can indeed contain odiferous molecules also characteristic of tobacco flavors. But those molecules appear to come from the breakdown of compounds present in grapes, not from any exposure to tobacco (and, needless to say, the tabanones in tobacco don’t come from grape-derived compounds).

Megastigmatrienone is more conveniently called tabanone. Or, more properly, megastigmatrienones are are more conveniently called tabanones, because the designations apply to a group of similar molecules. They seem to show up in wine because carotenoids – the highly pigmented class of antioxidant molecules you’ll recognize from it’s best-known carrot-colored member, beta-carotene – can become megastigmatrienones under appropriately acidic conditions. The precise pathway from grape-derived carotenoids to tobacco aromas remains something of a mystery. It seems that brandies, distilled from grape wine, end up with concentrated amounts of tabanones or precursors which then have an extra chance to develop into tabanones during barrel aging.

That mystery makes all the more interesting a recent study to quantify tobacco aroma molecules in Cognac and Armagnac**. Most of the (many) examples they tested contained some tabanones. Concentrations varied widely, but the Armagnacs averaged higher than the Cognacs and – evidently to everyone’s surprise – the aged rums thrown in for comparison ranked even higher than the Armagnacs. Much higher, in fact, even though the molasses from which rum is distilled doesn’t contain significant amounts either of tabanones or of the identified precursor molecules present in grapes.

So, why is this interesting?

  1. Tobacco aromas in aged spirits are evidently not just coming from molecules originally present in grapes.
  2. The oak barrels used for aging rum, as well as various brandies, probably contributes substantially to tobacco aromas in those spirits by leaching precursor molecules out of the wood and into the spirit and providing favorable conditions for their development.
  3. The researchers behind this study seem to think that their new-and-improved means for quantifying particular variants of tabanones could be useful for distinguishing Cognac from Armagnac, presumably to defend against passing one kind of spirit off as another. Looking at the enormous variation in tabanones between one kind of Cognac and another, or one kind of Armagnac and another, this suggestion seems frankly ridiculous. Chemistry backs up tasting experience: individual bottlings vary dramatically in the presence or absence of tobacco aromas as a defining characteristic. Yes, Armagnacs beat out Cognacs on average, but averages don’t help distinguish individuals when individual variation is so high. A more interesting use of this research, I think, is the starting point it provides for thinking about how barrel-aging adds to tobacco aromas, in spirits and possibly in wines. I suspect that the people who produce these spirits already have a lot to say on that point. Joining their knowledge with some well-placed chemical analyses could improve everyone’s understanding of how tobacco aromas happen and how to manipulate them.

 

* Ewwww.

**Camper English has drawn up a helpful comparison between Cognac and Armagnac at Alcademics.com.

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