09 May 2010

What Makes Wine Go Bad

In my family, we like to celebrate Mother's Day by sharing food, memories and discussing the latest findings in Applied and Environmental Microbiology.

Today we lamented the thankfully rare occurrence of tainted wine. It is a sad thing indeed when the anticipation of opening a new bottle and enjoying the first sip gets turned on its head by wine taken over by the devil. I call this a "bad batch" but people who know more call it "taint" and it happens to roughly 1 out of every 200 bottles. That is a big enough number to concern the industry; they have reputations to guard and profits to secure. Fortunately, chemists are on the case.

Analysis of tainted wines has revealed several chemicals that may be culpable, either individually or in concert. Where do these chemicals come from?

One source is the cork... it turns out that cork is an ecosystem to a variety of bacteria and fungi. This shouldn't be that surprising since cork is a living substance. It gets treated before being used to plug a wine bottle, but treatments vary and, apparently, are not successful 100% of the time.

If the wrong species of bacteria gets through and remains in the cork, it (or they) can react with the wine and produce the chemical(s) that give wine an "off" aroma and flavor. The implicated chemicals are chloroanisoles, chlorophenols and methoxypyrazines (good to know in case it comes up).

So that's how wine can go bad. Unfortunately, it's not possible to tell from looking at the bottle.

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