For example, I’ve heard bourbon is sweeter than other whiskies because it’s made from corn, rhum agricole is grassy because of sugarcane, and tequila is vegetal because of agave. What I understand is distillation concentrates alcohol because alcohol has a lower boiling point than water, so it’s heated and the vapor condenses on the other side. So how do flavors make it through? Also, aren’t sugars way bigger/heavier than alcohol and water? How do they make it all the way through?
In: Chemistry
Alcohol *and lots of other volatile molecules* have boiling points below that of water.
The volatiles come along for the ride, and many of them have distinct smells and tastes.
A lot of flavor compounds also have boiling points lower than water so they too will evaporate with the alcohol and condense on the other side.
Flavor compounds are also introduced during the aging process after distillation.
No distillation is perfect, and most spirits are 80-ish proof (that’s 40% alcohol and 60% water and other stuff). While more perfect distillation is possible in chemistry labs, that’s more expensive (not good for spirit company profits) and the result, something like Everclear, is much lest tasty to drink (not good for spirit company profits). The companies that make this stuff are in it for the money, and their recipes are all about a good tasting affordable to make product. That makes the so-so distillation they are doing just the right thing to do.
So is it possible to heat an islay like Laphroaig 10 to a certain point and “boil” off whatever it is that leaves that band-aid taste/smell and leave the rest of the deliciousness?
A lot of our perception of flavour comes from aroma in the nose, rather than taste on the tongue.
Our nose is sensitive to a lot of chemicals that easily turn to vapor, and some of these chemicals can and will come across during distillation. (They are already a vapor at room temperature, so at the boiling point of alcohol we’d expect them to be able to be vapours as well.)
Some might tend to come over before the boiling point of ethanol, around the boiling point, or after, and sometimes these are referred to as the ‘head(s)’, ‘heart(s)’, and ‘tail(s)’ of the distillation, respectively.
Things like sugar itself would not be expected to vaporise and so doesn’t end up in the final product of distillation.
Stick your nose over a bowl of soup. Do you smell more than the water? There’s your flavor. Smell is caused by aerosolized particles. It’s not a 100% separation.
I distilled a barrel of Guinness once and it made the most amazing smokey whiskey. I never understood why it isn’t commercially available.
They’re basically pure ethanol straight out of the still. Without aging, you’re basically drinking moonshine. For all reasons and purposes, the barrels are doing the heavy lifting as the spirit age in them. There is a specialized barrels industry that produces the right barrel to achieve desired flavors.
To be clear, some aromatic and flavor compounds do carry over from the distillation process and does matter, but it’s hard to even notice them prior to aging. As it ages, the compounds change over time and take on more flavor and aroma from the barrel, thus turning from clear, 120-ish proof ethanol compound to the 100-ish proof brown liquid we know.
Addressing the specific point of why sugars (bigger/heavier than ethanol and water) make it through, the oxygen in the OH group has two lone pairs of electrons and is able to pull strongly at the attached hydrogen, making the hydrogen quite positively charged. The result of this is that the oxygen from one OH group is strongly attracted to the Hydrogen from another. This is called hydrogen bonding, and is why molecules with an OH group (which of course includes water) tend to have significantly higher boiling points than similar size/weight molecules without one. This means that larger more complex molecules that are responsible for flavour can have a lower boiling point than water or ethanol even though the molecules are big.
Sugars don’t make it through because their boiling point isn’t in the right range. However, certain fermentation products have a sweet taste and have a boiling point closer to alcohol, which allows them to survive a round or two of distillation. This is true of other flavors as well.
As you distill more and more times, you get closer and closer to pure ethanol. This is why Everclear doesn’t taste sweet despite the fact that it is also made from corn, like bourbon.
However, most of the ‘sweet’ taste from bourbon comes from the barrel aging process. Bourbon, unlike other spirits, is generally aged in new charred white oak barrels. During aging, the ethanol and water in the bourbon extract flavor compounds from the oak, including some that make it taste ‘sweet’.
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