“So the question is, are you feeling fat or are you tasting fat?” said Richard Mattes, a professor of nutrition science at Purdue University who has done extensive research on the topic.
The texture of fat is difficult to distinguish from its taste, because for a chemical to be tasted, it must come into contact with the tongue and dissolve in saliva. The texture of fat is also difficult to imitate, as people dissatisfied with nonfat ice cream can attest.
In the study on CD36, researchers tried to limit visual and olfactory cues by lighting the testing area in red light and having the subjects wear nose clips.
“The evidence is growing [for fat as a taste],” Mattes said. “We have experimental evidence, but we have not definitively eliminated texture.”
Too hard to describe
In many ways, the discovery of receptors for umami and the prospect of receptors for fat, calcium and even carbon dioxide have called into question the traditional notion of basic tastes. Their characteristics are not as simple as, say, sweet or salty. Umami, for example — a word derived from the Japanese for “delicious” — is a complex taste whose chief effect is found in the depth of flavor of such foods as Parmesan, mushrooms and tomatoes.
“It might be that we have all these receptors but no words to describe what those receptors are like,” said Michael Tordoff, a behavioral geneticist at the Monell Chemical Senses Center in Philadelphia whose research focuses on calcium.
When asked to describe the taste of fat, many study participants said, “I don’t know.”
Fat is not the only taste that people find difficult to describe. Take calcium, another hot topic among taste scientists of late. Tordoff says that calcium has as much right to be considered a basic taste as sweetness or saltiness. The problem is that there is no word for what calcium tastes like.
“You’ll never know what calcium tastes like if you’re never told that’s what calcium tastes like,” Tordoff said.
“Part of it is a consequence of language,” said Jeannine Delwiche, who specializes in sensory science and psychophysics at Firmenich, a Swiss company that makes flavorings and perfumes. “For example, a lot of people confuse sourness and bitterness. You see that a lot with coffee and grapefruit. There’s not complete alignment in the way we use these terms.”
Problems like this have led some molecular biologists to believe that the whole concept of basic tastes is no longer useful.
“There’s no real definition for basic taste, and there’s a problem with assuming there is because it limits your experience,” Delwiche said. “We didn’t have a prototypical example of umami until it was derived from seaweed less than 100 years ago,” she said. She compared it with the description of some people’s hair as red, a term used by Europeans since ancient times. “Their hair is actually orange,” she said. But Europeans didn’t have a word for orange until the fruit was imported from other continents. “Without the prototype, we don’t form a word for the concept.”
Taste scientists say that discarding the traditional notion of basic tastes would open up more possibilities in taste discoveries. “I’m not sure we need to have a limit to our thinking,” Delwiche said.
Isolating the taste properties of fat could have important health implications. Since fat is an indicator of calorie-dense foods, the CD36 protein may help explain why some people consume more fat than others.
“If you taste fat more, you’ll be satisfied more quickly than someone who needs more fat to get the sensation,” Abumrad said. This might be applied to treating obesity by finding a way to increase sensitivity to fat.
But it’s not all about lowering our fat intake. The research can also help us better understand the role of fat in our diets. Fat is essential in the brain development of babies and children. It also helps the body better absorb the vitamins and antioxidants found in other foods.
“We live in a world where fat is stigmatized,” said Yanina Pepino, an author of the March study on CD36. “We forget that we depend on fat for life — for neurons, for cells. Fat is so important in our evolution.”
Wan is a freelance writer in Washington.