Just look at it… bloody marvelous.

Why does my beer smell of butter?

Imagine. You’ve got your hands on a beer at last. It’s been a long day. You’re tired, and you’re thirsty. There’s nothing you want more than to enjoy those first satisfying swallows of beer. But as you lift the glass to your mouth, what’s that you smell? Is it… is it butter!?

This is a sure-fire sign your beer is faulty. The problem is that it contains too much diacetyl. This is a malt-derived chemical that gives beer an aroma like butter. Some people also report aromas of butterscotch or movie-theatre popcorn. And it’s not just the smell. Diacetyl can also cause the beer to feel flat and slick on your palate. All in all it’s not the pleasant experience we expect our beer to deliver.

This beer looks lovely. Imagine how disappointed you’d be if it smelt of butter. Yuck!

Read more about off-flavours in beer here.

So how did this happen?

Diacetyl is present in all beer. It’s a natural side-effect of the fermentation process. Usually there’s so little you can’t even taste it. No harm, no foul. The problems I’ve described above only…