rancio , also sometimes known as “rancio Charentais,” is a difficult-to-define characteristic long noted in some very old cognacs: a set of aromas not obviously derived from the grapes it is distilled from or the oak it is aged in that have been described as reminiscent of truffle or cheese or nut oils. Rancio has also been identified in other spirits, although the idea will divide a room full of spirits tasters the way terroir or minerality will divide wine tasters. Ten or twenty years ago, to apply this very French term to a whisky seemed precious, even absurd, but malt heads such as Gary Regan, an early adopter of the term for whisky, have found that it applies to some of the oldest and most evanescent drams. See Regan, Gary. Use the word to describe a tequila, however, and its producer could well take deep offense, though that too may change with time.
As with most such terms, ask ten drinkers what rancio means and you will get ten different answers—at least. Alexandre Gabriel of Cognac Ferrand and Jean-Paul Vidal of the French Union nationale des groupements de distillateurs d’alcool have studied the development of rancio and its identification. See Pierre Ferrand.
Gabriel suggests that ketones are the primary precursors responsible for rancio development (others suggest that the principal one responsible is 2-heptanone, but it is always accompanied by others). See ketone. His research reflects experience and scientific rigor, but each cognac and Armagnac producer seems to parse these ephemeral matters rather differently. Gabriel differentiates four periods of primary rancio development, all in the barrel:
• 0–5 years, when almond, nougat, and port aromas are developing
• 15–20 years, when jasmine, narcissus, and Roquefort-cheese aromas develop and methyl ketones first appear
• 25–30 years, when a balsam character arises, leached from the wood
• 30+ years, fourth and final period, until the cognac gets too tannic to drink, with silky textures and increasing fruits, along with pepper, coconut, and other aromas, as well as a concentration of heavy esters
Other tasters speak of the same characteristics but appearing in a differing order, so either considerable subjectivity is at work, or there are differing directions of developments for differing producers. Unquestionably, grape-based spirits develop differently than apple-based spirits or grain-based spirits.
Interestingly, in wine circles, the lactone sotolon (which smells of maple syrup and fenugreek) is identified as a sole agent for rancio development, but it is likely that a reductivist mindset is at work when a single compound is considered the origin of so many different aromatic, flavor, and textured compounds. See
Buxton, Ian, and Paul S. Hughes. The Science and Commerce of Whisky. Cambridge: Royal Society of Chemistry, 2015.
Waterhouse, Andrew Leo, Gavin L Sacks, and David W. Jeffery. Understanding Wine Chemistry. New York: Wiley, 2016.
By: Doug Frost