Mind Power

How Your Nose Knows

By Ruth and Edward Brecher

“My, But this tastes good!” you remark as you take your first sip o piping-hot onion soup, salted, peppered, seasoned with herbs and garnished with cheese.

You’re wrong, of course. You mean that the soup smells good. Your sense of taste tells you only whether a substance is sweet, sour, salty or bitter. It is your sense of smell that reveals the true savor of the soup. Try sipping onion soup while holding your nose, or when you have a head cold. The characteristic flavor vanishes.  All that is left is a hot, some what salty liquid. By means of taste alone, you can barely distinguish between a food you love and one you detest.

Flavors reach the nose “through the back door”: they travel from the mouth down the throat and then up again along the air passages which lead to the nasal cavities. You “smell” when you inhale; you sense flavors when you exhale; otherwise the two processes are the same. Both depend upon our olfactory tracts-the nerve-rich surfaces which from the ceilings of your two nasal cavities. Each olfactory area is not about the size of a postage stamp and located so high in the nasal passages that, during ordinary inhaling, moderately odorous air may you see something whose odor you wish to sample, you sniff-and this carries the odor-laden air upward to the olfactory tract. There is no need to sniff while you eat, though, as you chew your food, warm vapors are released from it; the act of swallowing and the related act of exhaling pump these flavor-laden vapors upward toward the nose.

In general, the higher the temperature of a substance the more molecules are given off and the more intense is the odor. This explains why good cooks insist on serving dishes piping-hot. In certain respects, smell is the subtlest of our senses. A scientist can, with the help of costly laboratory aids, identify one drop of a chemical mixed with a million drops of something else. But with his unaided nose the same scientist, or anyone else, can instantly identify a highly odorous mercaptan – for example, that responsible for the stench of the skunk – even though each molecule of it is diluted with billions of molecules of air.

Although much work has been done in the field, odor specialists have been unable to identify any primary smells. Every natural odor, of flavor, most experts believe, is a blend of many. In coffee chemists have identified more than 50 flavor components, and suspect that there are many more. Therefore they speak of “flavor profile,” in which each component modifies your reaction to the others. A good cook uses this flavor profile instinctively. She adds spices and herbs in quantites too small to be indentified individually, yet sufficient to achieve a striking total effect. The goal is to have guests ask, “what did you put into this to make it so delicious?” rather than, “Mmmm.. ginger, isn’t it?”

The same sense which guides you in food selection also provides your enjoyment of flowers, perfumes, the odors of a garden on a moist spring day, of fresh-cut hay in the summer or burning leaves in the fall. It can summon out of the distant past an emotionally satisfying recollection of some early scene. A whiff of a particular perfume may transport a man back to the high school commencement party and his first girl. Why are some smells pleasant and some unpleasant? The answer seems to lie partly in the distant past of mankind and partly in our own experience. The stenches of rotting and of excrement are almost universally detested; they are warnings of possible contamination. And the door of the skunk is nauseating not only to humans but to animals as well.

Do we differ much from one another in our sense of smell? Certainly there is some variation. It is said that women have a more acute sense of smell than men, and that our sense of smell becomes dulled as we grow older-so that we are more likely to enjoy highly flavored foods like anchovies and pickled herring late in life . However, experts who have run thousands of taste and smell panel tests tell us that they are much more impressed by the similarity of smelling ability among people generally than by the differences.

It is widely believed that smoking and drinking alcoholic beverages dull our sense of smell. The evidence is not impressive. Professional coffee-tastes often smoke at their tasting ritual. It has also been reported that our sense of smell is most acute a when we are hungriest, and loses some of its sharpness after a meal. This may be a matter of paying more attention to smells when we are hungry. Exposure to a specific strong odor for a few minutes will dull your awareness of that particular odor; hence workers in certain industrial plants where a foul smell is always present soon lose their sensitivity to it. But even after a whole day in a beet-sugar factory, where a highly objectionable odor is present, workers can still distinguish other smells without difficulty.

Some scientists think we are gradually losing our sense of smell. They tell stories of primitive tribesmen whose noses are sensitive enough to be used in tracking game. But it is equally likely that our sense of smell is only lying dormant, ready to be used effectively whenever we choose to train it. A perfumer, after sniffing a flower carefully, can analyze its fragrance into numerous components and then blend appropriate substances to produce a scent barely distinguishable from the original. A wine-taster, savoring a fine wine, can sometimes guess from its bouquet not only the type of wine but also the vineyard from which it came and the year in which the grapes were grown.

The extent to which much “nosy” enjoyment can be developed is dramatically illustrated in the experiences of Helen Keller. Blind and deaf, Miss Keller was from an early age far more dependent on her sense of smell than the rest of us. The late Dr. Frederick Tilney once resolved to test her sense of smell on a drive from New York City out to Long Island. Mile after mile, Miss Keller was able to identify her surroundings by smell alone. “Now we are passing through grassy fields,” She said as the car skirted a golf course. “Here are trees,” she added as a wooded grove whizzed past, “and there is a house with an open fire on the hearth.”

Dr. Tilney had completely missed the house. Looking back he could see it, a wisp of smoke curling from its chimney.

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