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I was wondering about vodka vs. whiskey mostly. The way I understand it, a distilled beverage is created by heating a non-distilled beverage, say, beer, and then collecting and cooling the vapors.

Why would these vapors contain anything but alcohol and some water? Certainly the impurities that color, say, whiskey do not vaporize at the low temperatures involved? Why don't all distilled beverages taste and look like vodka (i.e. water and alcohol)?

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Two different aspects come into play here. For once, most of the whiskey aroma stems from aging the fresh destillate in oak barrels previously used to store wines, e.g. sherry. Colour an aroma thus, at least in part, stem from a slow extraction process using the fresh destillate as a solvent.

But thinking in other beverages, particular the clear fruit spirits, there's more in it. The key to a beverage that doesn't smell and taste just like ethanol but has a cherry aroma is the sloppyness of the destillation :) In the lab, a destillation or rectification is performed to isolate a particular compound from a mixture at a sharp boiling point.

In the production of alcoholic beverages, the destillation typically aims to obtain three fractions over different boiling point ranges.

  • At lower boiling points, methanol, acetone and ethylacetate are removed.
  • The upper range mostly furnishes long chain alcohols.

These two fractions aren't meant to be digested ;)

The central fraction, however, will contains all the fragrances, ethanol and water.

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    $\begingroup$ And the middle fraction, which contains mostly water and ethanol will also contain a lot of volatile organic compounds from the original fermented source, thanks to steam distillation $\endgroup$ – Ben Norris Aug 19 '14 at 10:38
  • $\begingroup$ Ben Norris: AFAIK, the steam distillation is "good" mainly for immiscible liquids. And according to my experimental knowledge (fruit spirits), the nice aroma comes very late in the alcohol fraction, at about ~25-30% alc. in condensate. $\endgroup$ – ssavec Aug 20 '14 at 5:57
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You compare incomparable. Vodka is distilled and immediately bottled and sold. Whiskey is stored for >3 years in wooden casks, often used for wine previously, thereby getting lot of fragrances from wood and also from environment (Scotch whiskey from islands, e.g.). The fresh distilled whiskey is clear colorless liquid. As for the color, 99% of the whiskeys contain added colorants, as the customers think that darker color means more matured and therefore more tasty spirit. AFAIK, the Ardbeg distillery does not add them that much, so this is the genuine whiskey color (more like white wine): http://thewhiskyphiles.files.wordpress.com/2014/07/ardbeg-blasda.jpg?w=339

The aromatic compounds are nevertheless distilled together with the spirit, so you can distinguish fruit distillates, Calvados, Williams, Kirsch, etc... These compounds (mostly esters) have boiling point somewhere between alcohol and water, thereby during batch distillation, you have to carefully watch the process and collect the smelly fraction, as it is immediately followed by acids.

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