Flavor is a multisensory experience, and aroma is a crucial but tricky part of flavor. To evaluate aroma, sensory scientists train volunteers to communicate what they are smelling.
DAVIS, Calif. — Can you describe the flavor of the last thing you ate? Not whether or not you liked it, but the sensation of eating it. Chances are, it's difficult to do so in much detail. And when you do manage to put the flavor into words, you may wonder how well others would understand what you are saying.
That's because flavor suffers from a language problem.
"In our culture, and in most cultures, we teach our kids to discriminate sounds and colors, we work really hard at that," said Hildegarde Heymann, a sensory scientist at the University of California, Davis. "We very rarely tell kids what things taste and smell like — we may tell them it tastes good or tastes bad."
"I may tell you this is really yummy, it tastes just like my grandma's apple pie; [but] my grandma may have used cinnamon and your grandma may have used cardamom and they are totally different apple pies, but we don’t go into that. We don't teach people to pay attention to their noses," she said.
Heymann's lab looks into questions about flavor often in wines, such as, how do wine and chocolate affect each other's flavors, or how do cabernet wines from Washington state compare with those from California, for instance. These questions can't be answered with "like" or "dislike". Instead, volunteers learn to pay attention to their noses and communicate what they experience. And the aromas they hone in on aren't always fruity, floral or pleasant sounding.
What is it?
Flavor is a single word that covers a lot of ground. The flavor we perceive arises not only from taste and aroma, but also the physical sensation food creates in your mouth. It's influenced by the appearance of what you're consuming, even the sound it makes as you chew.
Taste and smell may seem closely related, but in fact they are quite separate. Receptors on the taste buds of your tongue pick up taste, which comes in five distinct categories: sweet, salty, sour, bitter or umami (or savory). (Although some argue there are more.) An aroma, meanwhile, originates when receptors in our nose pick up volatile chemicals — those that evaporate easily — released by a substance into the air.
The two seem linked because aroma is picked up from the mouth when volatile compounds travel from the back of the mouth into the nose. Your saliva, the warmth of your mouth and the act of chewing all enhance the aromas that travel from the back of your mouth into your nose. As a result, it's easy to confuse the aroma for taste.
Learning to speak flavor
Heymann and her team often work with wine, and to get around the language problem, they frequently use a technique called Descriptive Analysis.
They assemble a panel of at least eight people, a large enough group to compensate for individual taste differences, and a panel leader guides them in creating their own vocabulary to describe the aromas in the wines or other samples they are given.
"We tend to do it by having the panel tell us what is going on and that is really like learning to speak language as a child," Heymann said.
After deciding upon the aromas they detect in the wines, the panelists each evaluate them. Other characteristics, primarily taste and mouth feel, require much less work before they are evaluated, because they come only in limited varieties.
To compare a set of 18 wines, say, the complete process would typically take five weeks.
During the training sessions, the panelists taste (then spit out) various wines, They come up with words to describe the taste differences between the wines. The panel leader must help them winnow down these descriptors, figuring out how to describe a characteristic someone describes as strawberries, and someone else describes as red berries, and someone else describes in yet another way.
This process isn't about liking or disliking; the panelists must objectively describe what they perceive.
The panel leader, a role often played by Helene Hopfer, a postdoctoral researcher in Heymann's group, brings in reference standards — actual items, sometimes floating in wine — to help the panelists agree on what they are smelling. [Do Wine Tasters Taste More Than Others?]
Setting the standards
When I visited the lab in December, Hopfer presented me with several such references in black wine glasses to prevent biases that might be prompted by the sight of whatever is floating in them.
"Swirl the glass a bit, then you take a sniff and you try to think what it might be," Hopfer instructed. "It gets easier the more often you do it."
The odor was, well, naggingly familiar, acidic and beyond that, very difficult to describe. A peek inside revealed peas and slices of green bell pepper floating in red wine. (When possible, the references are presented in a bland wine because the wine itself can affect the flavor.)
"If you would be on my panel you would say 'I smell bell pepper,' and I would give you three or four different versions of a bell pepper: a fresh bell pepper, a frozen bell pepper, a red bell pepper, and then you would say 'That one is not the one I am looking for, that one is pretty close,'" Hopfer explained.
After the group has agreed upon the aromas for the items floating in the wines, each member will evaluate the wines themselves (sans any peppers or strawberries floating in them) for the aromas, tastes, mouth feel and other characteristics, depending on the nature of the question they are exploring.
Mouth feel — like the heat associated with alcohol or the dry feeling that arises from something astringent — is perceived through a different neural pathway than aroma or taste.
For the final evaluation, the panelists go into tasting booths, where they rank each attribute for each wine on a sliding scale. They do this one wine at a time, taking breaks between wines and cleaning their palates with water or crackers. Here too, they must spit.
The data they generate is analyzed statistically and related to data on the chemistry of the flavors. [Chemist Grapple with Strawberry & Other Flavors]
A matter of taste
The panelists are often students from the viticulture (grape-growing), enology (study of wine) or food science departments at Davis. The first panel that Arielle Johnson, a graduate student studying flavor chemistry, participated in explored the effects of wine and chocolate on one another.
She found it intimidating at first.
"I had never done one before, and I was in a room with a lot of people who had been doing this for a long time," Johnson said. "But it was really interesting, sort of paying attention that closely to all the things I could smell in the wines and listening to all the things other people had to say, and then going back and seeing if I could get the same thing,"
While menus and liquor-store labels describe their wares in floral, fruity-type terms, wines can also bring to mind diesel, rubber, a barnyard, and other less conventional aromas. In small amounts, these can add complexity to a wine, in larger amounts, they are often considered defects. But even then, some people are still drawn to them.
"There are people who are like 'Oh, ashtray, I love it,'" Hopfer said. "I really have a problem with 'This is a good wine,' and 'That is a bad wine.'"
During the wine and chocolate panel, someone detected a particularly memorable aroma: Fecal.
"The proponent of fecal was saying, 'Well, actually, I kind of like a little bit of it,' and everyone else was saying, 'You can't call it fecal, it doesn't smell fecal,'" said Johnson, who did not personally pick up on that aroma, which was eventually voted down, she said: "I think we put something dirt or strawlike."