Science Questions

Why does my beer sometimes explode?

I sometimes brew my own beer. When I open a bottle of beer that I’ve brewed, sometimes it behaves nicely and fizzes up all over the place but this doesn’t seem to be correlated with how long the beer has spent in the bottle. Since I reuse the bottles I’m wondering, therefore, if some bacteria have got into the beer and they keep fermenting it in the bottle. Does this theory make sense and what other explanations might there be? Gregory Staradub, MIT

We put this question to Charlie Bamforth, Professor of Beer and Brewing at the University of California at Davis.  You can hear the whole interview here.

Well, there’s all sorts of potential problems with brewing beer yourself. The key secret to brewing good beer is hygiene, hygiene, hygiene. It’s always possible that there’s residual sugar that’s not been fermented properly in the fermenter, that’s left behind in the bottle. Sometimes they may be leakers and the CO2 may come out of the cap. There are all sorts of possible explanations.

October 2007