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Friday, November 14, 2008

Where to draw the line on old wine

Several years ago I gave a talk on design of experiments at a national conference of microbiologists in California. One of the other speakers in my session was an enologist (a scientist that deals with wine and wine making) from UC Davis – Associate Professor David Block. He helped me settle a debate in my family on how long one should keep wine stored after opening. Opinions ranged from indefinitely (years!) to less than 3 days as a guideline. My guess was 10 days at the max.

Naturally I thought of ways to put this to the test. My idea was to try a triangle tasting over time. Each taster is given three wines, two of which are the same. I saw this in a book I am read called The Drunkard's Walk, How Randomness Rules Our Lives. (By the way, the author thinks professional wine ratings are nonsensical for the most part -- purely random.)

However, after hearing from Prof Block, who like me is a U of Minnesota chemical engineer, I may not bother to experiment on aging wine because his answer fits my preconceptions (warning: technical details ahead!):

“The aging of wine is mainly related to the amount of oxygen in the bottle after it is opened, the amount of SO2 used by the winemaker for that particular wine, the wine pH, the amount of phenolics (more in red than white wines), and the amount of previous oxidation. So, for instance, if you only drink a small amount and put the bottle in the refrigerator, you are likely to see less oxidation than if you drink almost the entire bottle and leave lots of head space in the refrigerator.

My experience is that with sweet, dessert wines, I can leave them for months and they are still OK. This may be due to the winemaker adding more SO2 to decrease the chances of growth on the residual sugar. The SO2 can protect the wine somewhat from oxidation and production of aldehydes (typically associated with off-flavors or aromas).

Something like a sherry can be kept for a very long period of time at room temperature, typically because it is already oxidized during long barrel storage necessary to get the sherry-like characteristics (e.g. butterscotch, carmel, dried fruit aromas).

The effects of phenolics are a little more difficult to describe as they can be oxidized themselves, liberate H2O2 in reaction when they react with O2 (that eventually produces aldehydes), etc. However, it is generally felt that red wines with higher phenolics will last longer than white wines with lower phenolics. And...of course, all of these reactions are sensitive to pH and temperature.

That's kind of a complicated answer to your straightforward question...but it is a pretty complicated system. I keep off-dry white wines in the refrigerator for months. Dry reds and whites...probably less than a week. Sherries and ports and brandies...more or less indefinitely at room temperature.

Remember, that different people have different abilities to taste and smell various aromas and flavors, so one person's acceptable period may be different than a second person's period.”

So for the dry red wines I enjoy (tonight it is a boutique Syrah from Paso Robles California), I drink up the bottle within one week. That's my theory (with support from Prof Block) and I am sticking to it!

PS. Wine is fine for sipping and entertaining at the fancier soirees, but for an old-fashioned backyard barbecue it’s hard to beat a can of cold beer. The trick is keeping your brew cool on a steamy summer evening. Check out the results of this very enterprising and creative beer drinker who experimented on can cozies . The one made of rice krispies is unusual but I’d bet on a Thermos brand can insulator like this one that claims to keep your beverage cold ten times longer and 3 times longer than foam cozies.


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