Some chemical I can't remember the name of. It was part of an experiment for the biology part of my college course because apparently the presence of a certain gene defines whether or not you can taste it. As it turns out, I'm what's known as a "super-taster". That stuff tasted like a flash-fried scrotum that had been marinated in excrement for about a week beforehand. And the fun part is, because of my being a super taster, I was still tasting it for, and I'm not joking, about 4 hours afterwards.