June 11, 2007

Wine Chemistry

posted by philip in Wine

I spent Saturday afternoon cycling with a good friend of mine, Rodolphe Boulanger, who is President of an online wine retailer and a keen wine aficionado. Both of us studied Chemistry at University, and both of us have a large degree of skepticism over a lot of wine heresay. This time, we argued the validity of accepted wine storage best practices, namely: Controlling Temperature, Light, Vibrations and Humidity.

Temperature – True
Wine is a product in the middle of a chemical reaction. It starts off as grape juice, ferments and becomes wine, then gradually oxidizes and becomes vinegar. The warmer it is, the faster this reaction occurs. Too hot and you’ll cook the wine, which is irreversible. However, there’s not much difference between cold and too cold. Too cold just slows down the reaction, a good wine will therefore age slower, and tastes bad, so you need to allow it to warm up slowly.

In response to Stephen’s question on whether you can freeze a wine. The answer theoretically is yes, the cork may pop out as the wine expands on freezing, and you may get crystals (tartaric acid) precipitating out of the liquid, but these are harmless. There’s no reason to freeze a wine, but structurally it should remain unchanged.

Light – True
Light, especially sunlight (UV etc.), reacts with the colored chemicals in wine – you alter the color, you alter the taste.

Vibrations – False
Vibrations at the level we’re talking about (fridge motor etc.) do not affect chemical reactions. The only problem with vibrations is that it may kick up any sediment, but again, fridge motor vibrations don’t really do this. Putting a bottle of wine on top of a washing machine on spin cycle might do some damage, but thats it.

Humidity – True (for natural corks only)
This is true, but not for the wine. If the humidity gets too low, the cork will dry out and lose its airtight seal. That will allow air in and the wine will oxidize. For screwcaps and other airtight seal, the humidity is irrelevant.

by Wilf Krutzmann · June 11, 2007 at 3:40 pm

Just an observation, but wine does not necessarily or automatically become vinegar, even with an increase in the temperature. It requires a vinegar bacterium such as the Acetobacter aceti to start the acetification process.
For a good synopsis on this follow the link below to the 30 second wine advisor. Great blog, I have it bookmarked.

http://www.wineloverspage.com/wineadvisor/tswa030407.phtml

by philip · June 11, 2007 at 3:50 pm

Wilf

I just signed up for it too! If you’re a regular reader of that blog, you’ll be pleased to know we’re integrating their tasting notes into our site.

Philip

by Wilf Krutzmann · June 11, 2007 at 9:18 pm

Philip, when I said “great blog” I meant yours. I will check in regularly.
Cheers,
Wilf

by philip · June 12, 2007 at 7:48 am

Even better! thank you.

by Snooth Blog » Do imported wines age faster · July 5, 2007 at 2:02 pm

[...] blogged about what upsets wine a few weeks back. It got me thinking. I’ve seen how wines are imported into the country – [...]

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