About 30-odd years ago there was an editorial in The Wall Street Journal that said, simply, vodka is ethanol and therefore essentially the same from brand to brand, and that consumers should buy strictly on price. I knew that intuitively since I have taken just about every type of organic chemistry course offered (master's degree in chemical engineering). What do you say?
Your e-mail signature states that you are a PhD. This will be a first for me – attempting to explain chemistry to a much more qualified scientist.
Vodka in Canada, the United States and many other jurisdictions is indeed defined as a potable spirit with essentially no distinctive character, colour or odour. It usually comes off the still at 90-plus-per-cent alcohol (laws and methods differ from country to country), which in this case means 90-plus-per-cent ethanol in chemical parlance. The spirit in your glass tends to register 40 per cent, of course. The difference consists entirely of water, added prior to bottling.
So there are a few ways "flavour" can creep into your vodka.
One is from what remains in the distillate above that 90-plus-ethanol figure. There are what are sometimes referred to as "impurities" in the distillate, compounds that can be pleasantly redolent of the starches or sugar-rich plants from which the drink is fermented, such as wheat, barley and potato. Such non-ethanol ingredients will impart extremely subtle taste variances between brands.
Another other source of "flavour" is – as you may have guessed by now – the water used for distillation and dilution. This sometimes accounts for why many distillers make a point of bragging in their marketing pitches about the "purity" of their water sources, be it glacial, a mountain spring or a tap. There are minerals and possibly other ingredients in that water that vary in concentration from source to source, in the same way that one brand of bottled water, such as Evian, will be subtly different from another, such as Fiji. So, yes, you might be paying a significant premium for that pricey vodka mainly on the basis of the water source.
Filtration can make a difference too. Depending on the method, ingredients in the distillate or the water will be removed or even added by the filter surface.
Often when people speak of vodka's flavour, they're in fact talking about texture, which can vary from distinctively oily to dry. And this is sometimes achieved with sugars or citrus oil, compounds which, when mixed in trace amounts, may require no label declaration.
The Flavour Principle by Lucy Waverman and Beppi Crosariol recently took home top prize for best general English cookbook at the Taste Canada Food Writing Awards. Published by HarperCollins.