The Science of Vodka
by Darcy O'Neil on October 2010
The idea of the purest, cleanest vodka is one of the biggest marketing ploy's going. Every company is advertising triple distilled, quadruple distilled, and so on, to give you the impression that the vodka is the best distillate possible. Some companies even make the gimmick go to six or seven times distilled! So what makes one vodka special and another one not so special? What would be the best way to make an ultra elite vodka? Why does all of this matter? I'm not quite sure, but vodka is the number one selling spirit and prices for a bottle are climbing to the levels of single malt scotch and fine cognac. The majority of this is marketing, with image being everything, so it seems.
So if we are going to make the purest vodka ever, how would we do that? Well, first we need to look at the most important part of the vodka and that would be ethanol. This alcohol has been made for thousands of years by fermentation. Almost everyone knows that to ferment stuff you need yeast and a source of sugar, which usually comes from grains or fruit. I'm not going to spend much time on fermentation, but let's look at how these affect the taste profile of vodka.
When a source of fermentable sugar is selected it can have a big impact on the final vodka product. Even though the product may be distilled a quadrazillion times, it is still going to contain some congeners. So what is a congener you ask? This is the chemistry definition:
Congener is a term in chemistry that refers to one of many variants or configurations of a common chemical structure.
In laymen terms, a Congener is a general term for small molecules other than ethanol which are found in alcoholic beverages and provide "flavour". They include aldehydes, esters, and primary alcohols such as methanol and isoamyl alcohol. These molecules are usually present in the material that was selected for fermentation, or they could be a bi-product of fermentation. For example rye grain has a very distinct taste when distilled at low proof. This is because it contains certain oils and congeners that are soluble in ethanol, or have similar boiling points and are collected with the purified ethanol. The more strict the distillation process, the lower the congener levels and the purer the spirit.
There is a certain point where distillation cannot go any further. For example, no mater how many times you distill an ethanol-water mixture, you will never get 100% ethanol. This is because ethanol and water form an azeotrope at 94.68% ethanol. Now, what the hell is an azeotrope you ask?
Azeotrope - A liquid mixture of two or more substances that retains the same composition in the vapour state as in the liquid state when distilled or partially evaporated under a certain pressure.
This means that certain mixtures cannot be separated, by distillation, because they form a unique mixture that boils at its own unique temperature. Many compounds form azeotropes, and in many cases other organic molecules form an azeotrope with ethanol and it cannot be separated. This results in a less than pure distillate. However, for the purpose of vodka, this isn't a bad thing at all.
These impurities are what makes each vodka relatively unique. Since the congeners come from the fermentation material and the yeast, a distiller can control these by selecting the starting materials. This leads to the marketing people making wild claims about the base materials and the multiple distillations resulting in the finest, purest spirit ever created. Which really doesn't mean much, but many people latch on, believing they are getting something special. I'm not quite a true believer.
Vodka is a means to an end. By that I mean that it is the purest flavour carrier. For example, a vodka martini works because using a small amount of vermouth, in a base of ethanol, allows the drinker to detect delicate flavours. Straight vermouth isn't quite a delicate drink. In other drinks, the alcohol helps to balance out the sweetness, without affecting the flavour. Now, if I were to create a vodka company I would create 100% pure ethanol and then mix it with ultra purified water.
Is it possible to get 100% ethanol?
Yes, there are a couple of ways, the sexiest being "molecular sieve" technology. Basically, you start of with a good distillation process and distill until you hit the magic number of 94% ethanol. Then you use the molecular sieve technology to further rectify the ethanol to 100%. You take the 100% ethanol and mix it with the purest water available or pick some place in the world that has the image of pure water and mix it with the ethanol. Voila, instant vodka and a method that could make the marketing geeks go nutty!
There are a couple of other methods including using lime (calcium hydroxide) to dehydrate the ethanol, but this method requires adding a relatively impure mineral to the ethanol, resulting in a lot of possible contamination by trace organics and other chemicals. Doesn't sound sexy. The other way is solvent extraction. Still not cool sounding, well maybe cool, but not healthy sounding.
Over all I'm not a big fan of straight vodka. Vodka has its place, usually in a Kangaroo cocktail or fruity "martini" or when companies distribute flavoured vodkas. That is truly where vodka shines, as a carrier for flavours. On its own, vodka is just ethanol with some extra stuff, but when combined with flavours you can make a great drink. The marketing groups are where the mystique and creativity come from. Sometimes I wonder if a vodka maker discusses the process with the marketing department, before the manufacturing department.
Further Reading on Vodka topics: