Beer - It's the Yeast That Counts

It's a fun time to be a beer drinker because of all the inventive craft beers being brewed. There are some very interesting ones: oyster stout, mint chocolate stout... and coconut curry? Whether it's craft beer or your good ol' Budweiser, all beers require malted cereal grains and hops.

However, a key determinant of beer flavor is the yeast used in fermentation. That's because during fermentation, these one-celled fungi release aromatic molecules that flavor the beer.

But we didn't know why until now. It turns out the fungi are made to attract fruit flies which then carry yeast to other food sources and help them spread in the environment.

The scientist behind the study got a hint of this fifteen years ago when he rushed out of his lab for a bar leaving three flasks of yeast open. Upon returning, he found fifty fruit flies floating in the yeast that was engineered to make 100-times more of the aromatic molecules. And only two flies in the normal yeast. Naturally he thought yeast made molecules similar to ripening fruit to attract flies.

Fast forward to today and the same scientist is proving his theory. He found that a compound called isoamyl nitrate, which smells similar to overripe bananas, caused intense neural activity in the brains of flies. This shows yeast that produce these molecules are able to attract flies and can spread further into their environment.

In fact, by using colored yeast in order to track them, he found yeast that produced the aromatic compounds spread four times more frequently. Since yeast do not have any means of propulsion, hitching a ride to new food sources on a fruit fly solves that problem.

Happily for us, it also means good beer.