Dave Arnold, the well known and respected director of the Culinary Technology Department at the French Culinary Institute, was on hand to demonstrate the process using his Buchi rotary evaporator.
Following are some excerpts, courtesy of Popular Science:
They proceed with an unaged Glenlivet whisky first. Dave calls this “white dog” since it is totally clear in color with a taste vastly different than the 12 year aged final product which gets its color & taste from the wood barrels and time.
When you drink whisky, you’re drinking the wood it was aged in. That’s easy to understand in concept, but friend of PopSci Dave Arnold is here to spell it out for our taste buds: He has set up his laboratory evaporator and physically separated out the flavor components in a glass of Glenlivet so they can be sipped individually.
The Buchi rotary evaporator uses a process of vacuum distillation at room temperature to separate the liquids. Dave then produces what he calls “gray dog” using a 12 year aged whisky, but separating out most of the effects the wood creates ending up with a new variety entirely. Dave then proceeds to a 15 yr aged Glenlivet whisky and completes the same procedure, producing a “gray dog” version as well.
The 15-year-old variety, however, makes a great gray dog. It’s got back the balance that’s lacking in the gray 12. The paper and grain flavors are offset by a melony, citrusy sweetness. Innovative bartender Eben Freeman, sitting next to me, insists he tastes a briny umami flavor that reminds him of seaweed, but I’m not sure it’s there for me.
Side by side with the gray-dog component of the 15-year-old, we taste its other half, the amber-colored distillate that contains the woodiness. There’s not much to it besides its vivid color, really — a faint bitterness, a faint barkiness. It’s very low in alcohol compared to the original, and since alcohol is a prime carrier of flavor, that doesn’t help. Out of curiosity, I find an empty glass and mingle the 15-year-old gray dog with the 15-year-old wood component, reuniting the parts that have been separated. Almost magically, the familiar Scotch of liquor stores and bars emerges from two components that aren’t either really recognizable as Scotch.
They move onto a 18 yr aged Glenlivet, complete the distillation process again and agree this variety has the most complexity of them all. Overall, the taste buds have been awoken and challenged.
It’s been an enlightening drinking session, and we’ve only separated each Scotch into two parts. The rotary evaporator is capable of much finer fractionation than that; carefully wielded it could in theory pull out just the flavor component of Glenlivet that’s reminiscent of pear, or just the briny note, and so on. And that’s just using the device for separation. It can also be used to combine flavors, as Dave demonstrated in another Tales session, when he put fresh mint and caraway into the receiving end of the evaporator, in a bath of vodka. The co-distillation of those elements resulted in a new liquor, melding the fresh, volatile flavors of the plants in a never-before-tasted way, while leaving behind their grassier, heavier flavor elements. The key flavor compounds in spearmint and in caraway are stereoisomers of each other, R-carvone and S-carvone, so they play together in the mouth in an intriguing three-dimensional way.
We thank Dave Arnold and Popular Science for sharing this experience and helping to mark new territory on the common ground where cooking and science meet.