Ethanol is the
“good” type of alcohol that we consume, hopefully with party hats on! Congeners
are a mix of other alcohols, acids, fats, and so on. Congeners are what give
a spirit its unique taste. Some congeners are pleasant tasting while
others are nasty. Controlling which congeners end up in your bottle is a big part of the distiller’s skills.
Distillation
is what turns a mash of fermentation into something you might want to drink. Distillation might sound complicated and
wizard-like, but it certainly can be. The
basics of the concepts are very easy. Simply put, distillation is a way of concentrating
the good parts of the fermented mash, and leaving behind the less
desirable elements. Using heat to break
apart the various elements of the mash, a distiller can select just the desirable
components. Of course, sloppy distillation can leave lots of the bad stuff,
which makes hangover’s particularly nasty. That’s one reason why higher end
spirits are less likely to cause you a hangover after you consumed the same
amount of the cheaper spirit.
If you were to
take a pot
Everything
that is condensed that comes off the still before it reaches 212 degrees are
the “heads” of the distillation and need to be discarded. When the water temperature levels at 212
degrees the output is pure water or the “hearts” of the distillation. The collection of the distillate continues
until the temperature in the pot starts rising again. This means that the water is gone and the
other materials are turning to vapor. What
is collected at this point, what comes out from there on is called the “tails”.
Late 1700 to Early 1800 Pot Still |
The Still of
room temperature fermented mash is now heated up to 173 degrees the boiling
point of ethanol. What you’d observe is
the temperature is rising and pauses and then starts rising again until the temperature
for in the still levels off at 173 degrees. That vapor is simply the ethanol in
gaseous form. As long as ethanol is remaining in the
solution, the temperature stays at 173 degrees. Eventually
all the ethanol boils off and we notice the solution’s temperature starts
rising again. Once it starts to rise,
all the ethanol is gone from the mash and the collection needs to be stopped.
At this point different vapors other than ethanol begin coming off the liquid.
As with the water, the solution’s temperature stays steady till all the ethanol
has been vaporized off. Once this happens we’re left with just plain old water
and other dregs.
Laboratory Pot Still |
Chill the outside of this vapor tube cooling the vapor faster, perhaps bathing the tubing in some cool water for example. This is the essence of fractional distillation! How do you know which liquid is coming out of the tubing? That’s easy! Look at the thermometer. Knowing the temperature of the liquid you can infer what’s boiling, and hence what’s coming out of the tube in cooled form. If all you want is ethanol, only collect the liquid that’s coming out when the thermometer reads 173 F.
Of course, distillation is never quite so cut
and dried. While the ethanol is boiling off, the occasional congener molecule
(the flavor, you’ll recall) or water gets carried along in the rising ethanol
vapor. As a result, the cooled liquid you collect has more ethanol than you
started with, but also some amount of water and congeners. You can redistill the resulting mix to further
purify it. When a vodka advertises exactly how many times it’s distilled, this
is exactly what they’re doing, removing impurities and congeners with
each distillation run. On the other hand, congeners also contain the
components that give each type of spirit its distinct taste. The
congeners in tequila taste different than the congeners in rum. Using heat-based distillation, you can’t get
above 95% purity of ethanol, no matter how many times you distill. It turns out
that water molecules bond to ethanol molecules and more elaborate methods are
needed to strip the water out if you needed a higher alcohol percentage. This
is not coincidentally why Vodka by definition is 95% alcohol, as it comes off
of the still, also known as a “neutral spirit”.
Modern Column Still |
The beauty of
distillation is that it can be performed multiple times, each time further
concentrating the desired elements and leaving out the undesirable. Much of the
differences between brands of spirits come down to How many times the
liquid was distilled, what type of still was used and where in the boiling
process the distiller started and stopped collecting the finished product.
Some spirits
have legal requirements about the minimum or maximum alcohol content they must
be distilled to. Note that this is not the same as the final alcohol percentage
in in the bottle. Many spirits are distilled to much higher alcohol
percentages, aged in barrels, and then water is added to bring the final
bottled result down to more palatable alcohol levels, typically between 40% and
50%. Bourbon cannot legally be
distilled to more than 80% alcohol, but before it’s put into barrels, it must
be no more than 62.5% alcohol. Compare
that to vodka which is typically distilled to 95% alcohol. It’s easy to see that bourbon has many more
congeners in it so has far more taste than vodka ever will.
A huge part of
the spirit-making craft is controlling the distillation process. Knowing when
to start and stop collecting is just one part of the story. Every batch of
starting mash is different and the distiller’s craft is to know how to adjust
things to create an optimal distillate to get the final results they are
looking for.
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