The singer Madonna once said that men are like milk – if you leave them, they get angry. To what extent this applies to all men remains to be seen. Whether Madonna really said that is also unclear. But as far as milk is concerned, the sentence is correct. She gets really angry if you let her stand. The reason is the bacteria contained in the milk, which convert the sugar, the notorious lactose, into lactic acid. The milk becomes sour and at some point thick, because the milk proteins clump together in an acidic environment.
