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How does the way food looks or its smell influence taste?




© ISTOCKPHOTO/MIODRAG GAJIC

Dana Small, a neuroscientist at the John B. Pierce Laboratory in New Haven, Conn., and the Yale School of Medicine, sniffs out an answer.

In a classic experiment, French researchers colored a white wine red with an odorless dye and asked a panel of wine experts to describe its taste. The connoisseurs described the wine using typical red wine descriptors rather than terms they would use to evaluate white wine, suggesting that the color played a significant role in the way they perceived the drink.

Although sight is not technically part of taste, it certainly influences perception. Interestingly, food and drink are identified predominantly by the senses of smell and sight, not taste. Food can be identified by sight alone—we don't have to eat a strawberry to know it is a strawberry. The same goes for smell, in many cases.

To our brains, "taste" is actually a fusion of a food's taste, smell and touch into a single sensation. This combination of qualities takes place because during chewing or sipping, all sensory information originates from a common location: whatever it is we're snacking on. Further, "flavor" is a more accurate term for what we commonly refer to as taste; therefore, smell not only influences but is an integral part of flavor.

Pure taste sensations include sweet, sour, salty, bitter, savory and, debatably, fat. Cells that recognize these flavors reside in taste buds located on the tongue and the roof of the mouth. When food and drink are placed in the mouth, taste cells are activated and we perceive a flavor. Concurrently, whatever we are eating or sipping invariably contacts and activates sensory cells, located side-by-side with the taste cells, that allow us to perceive qualities such as temperature, spiciness or creaminess. We perceive the act of touch as tasting because the contact "captures" the flavor sensation.

Smells also seem to come from the mouth, even though there are no cells there responsible for detecting scents. Instead the sensation of strawberry, for example, depends upon activation of smell cells located at the end of the nasal passage. The information gathered by these cells is relayed to the mouth via a process called olfactory referral.

To demonstrate this phenomenon for yourself, hold your nose and place a strawberry jelly bean in your mouth and chew. You should detect sweetness and a little sourness, along with the hard (and then soft) feeling of the candy. With your nose held, however, you won't notice the strawberry odor. When you let go, though, you allow the odor molecules to travel through the nasal cavity to the smell cells, and suddenly the jelly bean has a strawberry flavor.

Acquiring information related to scent through the back of the mouth is called retronasal olfaction—via the nostrils it is called orthonasal olfaction. Both methods influence flavor; aromas such as vanilla, for example, can cause something perceived as sweet to taste sweeter. Once an odor is experienced along with a flavor, the two become associated; thus, smell influences taste and taste influences smell.

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