Scientists believe that in addition to sweet, sour, salty, bitter, and umami, there is a sixth taste — "oleogustus," which is Latin for "taste for fat." However, according to a new study in the journal Chemical Senses, it isn't a pleasant kind of fatty taste, but something a little more rancid. Rick Mattes, a professor of nutrition science at Purdue University and an author of the study, explains to NPR: "It is a sensation one would get from eating oxidized oil."
When subjects were given samples of bitter, umami, and fatty tastes, they "sorted fatty acids in a league of their own" even though up until now, there was no name for such a taste. Mattes tells Time that the fatty acid taste is "awful." The mouthfeel humans typically associate with fatty foods is due to triglycerides — a "molecule with three fatty acids," — that doesn't actually have a taste but is more about texture. Fatty acids on their own in a high concentration leave an unpleasant taste in the mouth.
Mattes says that "oleogustus" serves more like a warning system, similar to bitter. However, in small concentration levels it can be pleasant, just like how people tend to enjoy the bitterness of wine and coffee. Just don't go expecting entire restaurant concepts to be built around the taste, akin to say, Umami Burger.