Question re. whiskey distillation

[Keith Talent]

Yeah, I should probably know this, but here goes anyways. The only thing worse than being ignorant is being ignorant and not wanting the become educated.

How does the distilation process transfer the intrinsic flavour profile from the mash to the finished product? I assume it's because as the alcohol is evaporating, small amounts of chemical compounds that carry the flavours also go up the condensor?

I dunno, anyone hazard a guess? Shouldn't it be pure ethyl going up prior to the water vapourizing?

[jsolomon]

Keith, you're on the right track. However, it isn't going to be pure ethanol going up the column unless you're boiling pure ethanol.

The reason the flavors travel up the column is that they have a small, but appreciable vapor pressure at the given temperature they are distilled (and tasted). What this means, is that if you took a sample of flavor compound X, cooled it to absolute zero and placed it in a complete vacuum, then raised it to room temperature, or distillation temperature (85 celsius for the sake of argument), the once perfect vacuum would have some small pressure of gas in it due to a portion of the flavor compound going into the gas phase. It's the same process that allows sweat to cool us even though our body temperatures are much lower than the boiling point of water. The water (and flavor compounds) still evaporate, just at a lower rate.

It is safe to assume, however, that the effluent going up the column may be highly enriched in ethanol or other compounds, as compared to the mother liquor.

edit to add more information

Edited January 14, 2004 by jsolomon (log)

[Keith Talent]

Thanks for the quick response and clear answer.

[Mayhaw Man]

You got it right in the second paragraph.

Flavors are transferred along with the alcohol that is distilled off. In a post still situation more are transferred than would be in a column distillation.

In a classic Bourbon rig there is the main still, a feed from it to a secondary still (often called a thumper box, due to the noise the steam causes as it glugs up through the mash in the second unit), and then a cooling coil.

Many kinds of commercial liquor (vodkas, some rums, and other spirits) are made in a column distillation unit that pretty much draws off the steam at just the right point. These units are very efficient, but are not used that often in the production of spirits that are considered to be more flavorful, as the column does not transfer nearly as much of the essence of the beverage being distilled.

Multiple distillations under pretty good control pretty much strips out all of the flavor from any spirit. This is how vodka is made (Newtral Grain Spirits), it can be made from damn near anything as it's flavor profile is to have no flavor (or very little, I am not looking for an argument from you expensive vodka drinking guys )

Hope this helps

[Gary Tanigawa]

Follow-up question: I would have expected that the distillate is high proof. If this is what goes in the cask for ageing, then why are cask strength bottlings of relatively modest proof? I remember reading that the about 40% alcohol levels in most bottlings is achieved by dilution with water, but is there also a dilution step before whisky is put in the cask?

TIA for any clarification you can provide.

[Mayhaw Man]

In virtually all cases with all spirits (I know that there are exceptions, but I don't think that there are that many) the spirit is proofed back just before bottling and after blending (in the case of bourbon and I am guessing other blended spirits).

Watering back in the aging stages would be very inexact, as much evaporation occurs during aging. Taxes in the US are based on abv and distillers are very exact in what goes into the bottle, as taxes are much higher than the price of distilled water.

[QuinaQuen]

How much water the distiller adds often depends on how long they intend to age the booze in wooden casks. In the case of Mezcal, at least, cask aging demands a little bit of dilution to minimize the leaching of flavor-bearing particulates. Since the only aging that counts is actually the controlled capillary action of fluids and trace amounts of particulates through wood fibers, alcohol-borne particulates draw off too quickly for easy control. The addition of water helps to slow this process so it can be easily controlled.