We classify food as sweet, sour, salty, bitter or umami, but a new paper published in the journal Chemical Senses argues that we’re missing another basic taste: fatty.
It’s called oleogustus, and it’s the unique taste of fat, says Richard D. Mattes, distinguished professor of nutrition science at Purdue University and one of the authors of the study. “I can’t use any words that exist, so we’re forced to make it up,” Mattes says. (The Latin translation of oily or fatty taste is “oleogustus.”)
There’s no one definition for what makes something a basic taste, but Mattes thinks of it as meeting several categories: the stimulus should have a unique structure, it should bind or interact with a unique receptor, it should be carried by the taste nerves to the central nervous system where taste information is decoded, and it should have a particular function.
Mattes and his colleagues wanted to see if a group of people classified “fatty” as a taste that is unique from the basic tastes of sweet, sour, salty, bitter or umami. They fed people a series of solutions, plugged their noses to control for odor and asked them to sort them into similar or dissimilar taste categories.
People indeed separated fatty acids into a tight group; when they were given samples of bitter, umami and fatty tastes, they sorted fatty acids in a league of their own, even though there isn’t currently an accepted category or name for the taste.
“It’s been very difficult to figure out if people really view this as unique sensation, because we have no word for it,” Mattes says. “It’s pretty strong evidence that they are, in fact, perceptually distinct.”
But lest you associate the taste category with a delicious slice of greasy pizza, Mattes has some bad news. “Fatty acid taste is awful,” he says. “We think it’s more of a warning system.” We might be able to distinguish a fatty taste, but it’s not the type of fatty taste we know and love. The creaminess and viscosity we associate with fatty foods is largely due to triglycerides: a molecule with three fatty acids that isn’t a taste stimulus, but rather a mouthfeel, Mattes says. Triglycerides also deliver fat-soluble flavor compounds, Mattes says, but that flavor isn’t the true taste of fat.
To get a sense of what that tastes like, imagine heating your fryer for a good long time and tasting the food you cook in it, Mattes suggests. It won’t be pleasant, and you certainly won’t want to eat it. “The food industry has known about this for a very long time, and they go to great efforts to keep concentrations of these fatty acids below detection thresholds, because if you can detect them you’re likely not to eat the food,” he says. But in small concentrations below detection levels, the taste can be pleasant—just as we enjoy the bitterness of wine, chocolate and coffee, Mattes says.
Classifying a new taste could help us understand our food better, Mattes says. “If you understand the workings of a sensory system, you can use them for purpose,” he says. “Whether that’s to improve the quality of the food supply, the safety of the food supply, reduction of cardiovascular disease, treat taste disorders, there are any number of possibilities here.”