I was recently at a course run by Steve Plowman of Hallertau Brewery on how to identify faults in beer.
It was a brilliant exercise which demanded a lot of your nose and palate as some of the so-called “off flavours” in beer are so subtle. And what’s “off” to one person is regarded as a relatively nice character by others – such as diacetyl, which can taste a bit like buttered popcorn. In the right beer it’s an asset. In the wrong beer it’s more like rancid butter than a movie snack.