New research in the June issue of the American Chemical Societys Journal of Agricultural and Food Chemistry suggests hydrogen bonding as the cause of taste differences amongst various vodka brands. I’m not entirely convinced. I’ve discussed hydrogen bonding here on Associated Content before, and discussed how it can result in some pretty amazing transformations, such as those found in Jello. The researchers make the case that ethanol, which is present in the vodka, can act as one half of the hydrogen bond, with water (present in the vodka) acting as the other half. The formation of the hydrogen bonds forces the water molecules directly surrounding the ethanol molecules into a cage-like environment that has some rigidity and structure to it. It doesn’t become completely solid, obviously, but it’s more structured and ordered than a liquid would normally be.
The articles authors suggest that it is this tenuous cage-like structure of water and ethanol molecules that lies at the heart of the vodkas taste. It is no surprise to anyone that different brands of vodka taste differently. More expensive vodkas tend to be “smoother” and contain less harsh flavors, whereas a cheap vodka may have a strong medicinal taste and be quite difficult to drink unless its mixed with other flavors. That is why you rarely see high-end vodkas being mixed into a daiquiri or other type of strong, fruity drink; the “pureness” of the more expensive vodkas is completely besides the point if its delicate flavor is overwhelmed with orange juice. If you want to make a mixed drink, any brand of vodka will suffice; purists who insist on drinking vodka straight will opt for the more expensive brand.
Until now, researchers have always believed that it was trace amounts of impurities in the finished vodka product that were responsible for the differences in taste. Many cheaper vodkas are bottled and sold immediately upon production, and harsh-tasting short-lived chemical species don’t have a time to settle down before they are ingested. More expensive vodka brands are stored for a length of time before sale, meaning that all of the strong chemical intermediates have a chance to degrade before tasting. This new research from Ohio would tend to indicate that impurities have nothing to do with the taste experience, and it is simply this arrangement of water and ethanol atoms that is to blame for a vodkas taste. It makes me wonder how they tested the qualitative “taste” component of their experiments; I do not doubt that they had many volunteers for this phase of the research.
The report goes into some detail regarding the spectral patterns of each vodka sample and linking this patterns to a different arrangement of the caged water molecules in each different sample. I do not doubt that different brands of vodka, with their different impurities and trace components, each showed a slightly different spectrum. However, personally I think it’s a bit of a large jump to say that a vodkas microstructure could be linked to brand preferences based on taste. At most, I would say that a vodka’s microstructure could perhaps be used as an internal quality control measure; each distiller could monitor each new batch of their vodka (using spectroscopy) and only bottle the product once it matched a standard “reference” sample of their vodka. That would ensure that each batch of vodka tasted the same. However, it still doesn’t prove that the structure of the vodka causes the taste.
It seems much more likely to me that a vodkas impurities cause differences in the taste. I believe this to be true because of a very simple experiment that I can run in my own kitchen. If I take the worst possible tasting Vodka – the very lowest of the low in terms of cost or culinary experience – and filter the liquid through a water filter such as the one many people have attached to their kitchen tap, I find that the taste of the vodka is much improved. This is a common technique, well known to college students the world over; filtering cheap vodka through a water filtration device dramatically improves the taste, removing the harsh components. It succeeds because a water filter consists of activated charcoal, which has an enormously high surface area and which irreversibly adsorbs the trace contaminants while allowing the alcohol and water molecules to flow through unimpeded. Try it for yourself, if you like.
If the cage of hydrogen bonding around the ethanol molecules was truly to blame for the taste of the vodka sample, then filtering it through activated charcoal (which allows both ethanol and water through, thereby preserving the ratio of alcohol to water and therefore preserving the cage structure) shouldn’t affect the taste at all. But, it does. It improves the taste, and keeps on improving the taste each time that I pass the vodka through the filter (up to a point). This improvement has nothing to do with a rearrangement of the hydrogen bonding network – it has everything to do with the removal of contaminants. The published scientific article is a little bit misleading. It’s interesting that the structure can be measured using spectroscopy, and it may help vodka companies improve upon quality control, but I don’t believe for an instant that it has anything to do with taste.