A New Taste Sensation: Starch

Imagine for a moment the taste of fresh-baked bread, fried tortillas, or steaming basmati rice. In almost every culture, there’s a starchy staple central to the diet: the carbohydrate. Now there’s evidence that carbohydrate-rich foods have a unique taste that joins the short list of tastes that we can sense on our tongues.

[caption caption="OSU sensory scientist Juyun Lim and graduate student Alexa Pullicin prepare to test samples of starchy foods in their work to expand understanding of our sense of taste. (Photo by Chris Becerra.)"] [/caption]

Tasting food, it turns out, involves more than just salty, sweet, sour, and bitter. A few years ago, umami was added to the list, as the savory, meaty taste imparted by glutamate. Now, Juyun Lim has discovered a possible sixth taste: starchy.

“Every culture has a major source of complex carbohydrate,” says Lim, a sensory scientist in OSU’s department of food science and technology. “It makes sense that we should be able to taste them.”

Complex carbohydrates are huge molecules, made of long chains of sugar molecules. Up to now, food scientists assumed carbohydrates would be too large, too complex, to be tasted; a “key” far too large to fit into the small “lock” of a taste receptor.

[caption caption="Samples are chemically analyzed as well as evaluated by a panel of trained tasters at the Center for Sensory and Consumer Research in OSU’s Department of Food Science and Technology. (Photo by Chris Becerra.)"] [/caption]

Remember the middle-school experiment that had you spit on a cracker and watch it dissolve? Saliva contains an enzyme that breaks down starches into shorter molecules and turns the cracker to mush. Because enzymes in our saliva break down starch into shorter chains and simple sugars, it was assumed that we detect starch by tasting sweet.

Lim tested some of these relatively shorter carbohydrate chains with a panel of taste testers who reported a particular, floury taste in the solutions. “They identified the taste as ‘starchy’,” says Lim.

Lim’s team set to work to confirm that the starchy taste is uniquely recognizable, that it triggers a physiological response, and that it has its own set of taste receptors. So far, Lim and her team have confirmed the objectively recognizable taste and the triggered response; they continue to search for the starch receptors.

A verifiable primary taste must also be independent of smell, Lim says. Recall having a stuffed-up nose. Everything tasted bland. Smell is a big contributor to what we think of as taste. When you hold your nose (as Lim’s panel of tasters must do), you perceive basic tastes; smell adds character, so you can perceive the difference in, say, raspberries and blueberries.

[caption caption="Listen to Professor Lim about starchiness, on OPB's Think Out Loud. (Photo by Chris Becerra.)"][/caption]

“Our ability to taste things is more complex than once thought,” Lim says. Her work is part of an increasing number of investigations into other potential tastes, such as fats. She’s exploring a new frontier of taste that extends beyond the boundaries of what was once thought to be the tongue map, with four regions identified by four tastes. The tongue can register all these tastes in all its regions, Lim says. And she and her colleagues are discovering even more that can be registered by our remarkable sense of taste.