Saturday, January 31, 2015
Filtration: a Way to Improve Whiskey, or Destroy It?
Filtration is a part of whiskey-making that is rarely discussed. Virtually all whiskeys are filtered in some way before bottling. Mostly cosmetic, it is the last chance to make sure your whiskey glistens on the shelf.
Filtration also affects flavor. Some believe that's a bad thing and a few whiskeys choose to be slightly less beautiful so they can be slightly more flavorful.
The manipulative filtration of whiskey turns out to be a special skill of Michter's Willie Pratt, which he demonstrated through ten tastes of a 10-year-old rye whiskey Michter's was preparing to bottle. By varying the filter material, its density, the use of charcoal, and other factors, he produced ten distinctly different flavors from the same whiskey sample. The tasting panel's job was to select the one that showed best.
Everyone does this sort of thing, Michter's was just nice enough to provide a demonstration.
'Rectification' means to fix or correct. In the late 19th century, 'rectifiers' bought whiskey from distillers and 'fixed' it, i.e., they made it more palatable and, therefore, more marketable through blending, redistilling, filtering, and flavoring.
Some rectifiers took good whiskeys from different makers and batched them together into a product greater than the sum of its parts. Others created what came to be called compound whiskey which was, in fact, not whiskey at all but neutral spirit flavored to resemble whiskey. In those days before truth-in-advertising regulation it was passed off as the real thing, much to the chagrin of whiskey purists.
All of these techniques still exist but are regulated and must be disclosed when used. Filtration is the exception. It has always been considered a legitimate part of the production process. Since some kind of filtration almost always takes place as one of the final steps before bottling, it doesn't have to be disclosed. Even when it is deliberately used to alter the flavor of the spirit, the producer does not have to reveal what was done, how it was done, nor even that it was done at all.
The most ubiquitous type of filtration is chill filtration, the purpose of which is to remove certain fatty acids that can cause the whiskey to appear cloudy, especially when the bottle is cold. The whiskey is cooled to about 32° F and passed through a fine filtering medium (e.g., silk), usually coming into contact with activated carbon. This is supposed to have only a minor effect on flavor but it can be manipulated to deliberately affect taste in a significant way.
One reason filtering is not regulated is because it is a subtractive process, taking flavor (and color, odor, etc.) out, but not adding any. However, in the complex mix that is a whiskey's flavor, the elimination of one flavor can highlight those that remain. Long thought to mainly diminish a whiskey's flavor overall, skilful filtration can alter a whiskey's taste (presumably for the better) more than you might think.
Skill in the art of filtration is important for anyone who deals in older whiskeys, which in the case of bourbon and rye is anything that has spent more than a decade in the barrel. Old bourbons and ryes have their charms but because they are aged in new barrels, wood flavors tend to overpower, beginning in about year ten. The older a whiskey gets the more tempting it is to tone it down a bit through filtration, but an unskilful job can ruin the whiskey with blandness. Rectify a whiskey too much and you get vodka.
There is a subset of bourbon and rye drinkers who subsist almost entirely on whiskeys in their teens and twenties. Unless a whiskey's maker states that it is not filtered, it probably is, and a denial of chill-filtering doesn't tell you what is being done to it at room temperature. Presumably, the drinkers of these whiskeys want them to be all that they can be and if they can be improved by a little filtration, why not? Or maybe that's not how they feel, but that's how it is.