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Wine Glasses, Oxygen and Phenolic Compounds

The matter of wine glasses and how important they can be in the appreciation of all wine, not just fine or expensive bottles, is not a new subject. Recently, however, the results of fresh Kari Russellresearch has brought the matter to the fore once more. The research, performed by Kari Russell (right), a Food Science and Technology major at the University of Tennessee, involved an assessment of the effect of three very different wine glasses on levels of phenolic compounds in an unspecified Merlot. Phenolic compounds have received a lot of attention from the press in recent years, having been plucked from obscurity following the proposal that they are responsible for some of the health benefits of drinking red wine.

In the study wine was poured into three receptacles - a Bordeaux glass, a martini glass and a Champagne flute. Russell measured the levels of a number of phenolic compounds before and after pouring. One compound in particular - gallic acid - was of interest, as levels rose following the pour. Russell presumed that this was because of the conversion of gallic tannins to gallic acid as a consequence of the pouring action. Subsequent analysis revealed that within 10 - 20 minutes, levels of gallic acid in the flute and martini glass remained high, but levels in the Bordeaux glass fell. As it is known that phenolic compounds change when in contact with oxygen, Russell hypothesised that this was most probably due to the Bordeaux glass having a greater surface area of wine in contact with the air.

As a follow-up, Russell transferred the three wine samples to plain beakers and presented them to a group of students for an assessment by taste. The subjects could distinguish no difference between the samples, which I find hardly surprising. Just the transfer from glass to beaker, as well as the time spent in the beakers themselves, will have had some effect on the chemistry of the wine. There's also nothing to suggest, in my opinion, that a change in just one of many phenolic compounds should have an appreciable effect on taste.

So what's my take on all this? Well, I have several points to make.

Firstly, I think choosing a suitable wine glass is of great importance. I do believe that using the right glass can have a significant effect on the pleasure derived from a wine. There are a number of basic qualities that make a glass worthwhile, and put simply these are; size (good enough to hold a portion and swirl without spilling), material (plain, clear glass is the bare minimum - although lead crystal is finer), a stem (to avoid holding the bowl) and importantly, shape. This latter characteristic is most important - wine glasses should be wider at the base, to maximise the wine-air interface and improve release of aromas - and more narrow at the rim, to concentrate those aromas towards the nose.

Secondly, I do not feel that the ownership of dozens of different styles of wine glasses is necessary to enjoy wine to the full. I happily get by with just six different types of wine glass at home, although they are of high quality, made by the Austrian manufacturer Riedel. For someone with less of a passion for wine, however, just three styles - for red, white and sparkling - would probably be sufficient.

Finally, what does Russell's research tell us? I am disappointed more was not made of the proposed reduction in gallic tannins that resulted from pouring the wine. Wine lovers have long used decanting, with a good splash or two during the process, to soften up young, tannic red wines. This first finding lends weight to the notion that a vigorous pour may alter the tannic profile of a wine, providing consumers of immature claret with a hint that there might actually be some scientific evidence for what they do! As for Russell's main finding, however, I do not think it is of any great consequence. This finding is not due to some mystical effect of the glass on the wine, but rather it is simply confirmation that wine changes when exposed to oxygen. The wine with the greater area of wine-air interface in the study showed a greater change than those with smaller areas of interface. The fact that wine changes in response to oxygen shouldn't be news to anyone - just leave a glass of wine out overnight and then taste it the next morning - it's likely to be unpalatable - thanks to changes brought on following exposure to oxygen.