Nose and Tongue Learn to Team Up

The aroma of food helps you taste it--that's why even the spiciest of meals can seem bland when you have a stuffy nose. Now researchers have found that traces of scents and flavors too faint to distinguish by themselves can be tasted when combined. But this synergy may be an acquired taste, as the brain appears to only recognize chemical combos often found in food.

A chemical must be strong enough to tingle the taste buds in order to impress the palate. But if two flavors, both below this threshold, are combined, people notice. This seems to be true for any combination of flavors, and they add up; for example, a mixture that contains 24 flavors, each at 1/24th the concentration necessary to be detected, will leave a taste. The mix may taste strange, but a tongue can tell it from water.

But does the nose factor into the equation? To find out, a team led by psychologist Pam Dalton of the Monell Chemical Senses Center in Philadelphia--an independent institution affiliated with the University of Pennsylvania--combined benzaldehyde, a compound present in cherry and almond flavors, with two other flavors. One flavor, saccharin, is sweet--a taste often combined with benzaldehyde in candy and soft drinks. The other flavor, that of monosodium glutamate (MSG), is usually added to savory, salty foods.

The subjects held a half-threshold solution of one of the flavors or water in their mouths while sniffing a half-threshold shot of the benzaldehyde scent. When benzaldehyde and saccharin were combined, people could detect the mix. But when benzaldehyde was paired with MSG or water, the team reports in the May issue of Nature Neuroscience, subjects couldn't taste anything--even though the dose was equally strong. Dalton speculates that the brain might be more sensitive to familiar combinations.

Psychologist Joseph Stevens of Yale University says the study provides "pretty good evidence" that the brain learns to recognize subtle combinations of scents and flavors, and that experience influences what you can detect. But to prove that, he says, more combinations will have to be tested. Wine tasting, anyone?