March 25, 2000

When the nose doesn't know: Cornell scientists develop standard spectrum of smell to separate 'ahhh' from 'ugghh'

SAN FRANCISCO -- Distinguishing the difference between the aroma of pepperoni pizza and boiling cabbage is not as simple as it seems for everyone. Some people have a heightened sense of smell and can be overwhelmed by aromas. And some suffer from smell blindness, a condition appropriately called "anosmia," that could make the cabbage smell like a four-star restaurant.

But, who is who? In the commercial world, how do you distinguish between those with perfect sniff pitch and those with none? Cornell University food chemists are finding out by standardizing the spectrum of smell.

Jane Friedrich, Cornell doctoral candidate in food chemistry, is developing sniff standards in the laboratory of Terry Acree, a Cornell professor of food science, at the university's New York State Agricultural Experiment Station in Geneva, N.Y. "Let's say you smell an essence oil like jasmine, which is a pure smell. Your ability to smell that jasmine is based on a small combination of olfactory receptor proteins. Those proteins produce a pattern your brain would recognize," she says. But even for finite aromas like jasmine, people smell it in different ways.

Friedrich presented her research into smells, "Selecting Standards for Gas Chromatography Olfactometry," at the American Chemical Society national meeting today (March 26) at the Moscone Center, San Francisco.

One reason for the large variation associated with olfactory acuity is due to a phenomenon called "specific anosmia," said Friedrich. Simply, this is smell blindness, or insensitivity to the odor of a chemical or group of chemicals in people with otherwise normal olfactory sensitivity. Specific anosmia poses a challenge to researchers because it can distort data in sensory research labs.

Friedrich noted a classic example of this sensory-test problem from a study performed at the Western Regional Research Laboratory in Albany, Calif., more than 30 years ago. Test subjects sniffed isobutyric acid, which smells like dirty socks or an unclean goat to most people. But there were two testers who sensed the isobutryic acid had a "very pleasant fruity odor - like apples." Experiments later revealed that the wayward individuals had a specific anosmia to isobutyric acid, and the fruity smell they detected were the byproducts and impurities usually found in commercial samples of the acid.

"If a company wants to make pine cleaner for bathrooms and inadvertently uses a person on the smell panel with an anosmic sense of smell, that person may barely perceive the alpha pinen (the active chemical responsible for the smell). This means that the rest of the consumers will think it smells too piney," said Friedrich. "That's a problem."

Using a selective and sensitive bioassay for smells based on gas chromatography olfactometry, called CharmAnalysis TM, Friedrich and Acree have investigated the compounds responsible for specific anosmia. The researchers now are attempting to correlate sensitivity to the chemicals to the olfactory receptor genetics. In short, people can now be tested and categorized for their valuable acumen by sniffing a broad, standard aroma set - in a few whiffs. The set will allow laboratories easily to screen out individuals with specific anosmia.

Friedrich used standard tests to sort out her original testing subjects. She screened 10 people, with each testing period taking about 3 weeks, or 30 weeks of testing in total. Friedrich and Acree believe that they can now accurately place people in three categories: hyperosmic (very sensitive), hyposmic (the baseline category) and anosmic. "This will help other researchers conduct analyses," said Friedrich. "Our goal eventually is to get the testing down to three sniffs."