TEASING OUT THE TEXTURE OF TASTE: SENSORY EVALUATION AT THE UNIVERSITY OF ARKANSAS

FAYETTEVILLE, Ark. - The people who come to eat in Jean-Francois Meullenet’s laboratory participate in some unusual mealtime rituals. They sit on chairs in partitioned booths that sport computers and receive their food through a small hole in the wall. They are instructed not to have mealtime conversations with their neighbors. Sometimes the appearance of their food is masked by a red light.

After eating, they gather around a table in another room to discuss what they have just consumed.

The party of nine people who come four days a week to dine in Meullenet’s laboratory, housed in the University of Arkansas’ Department of Food Science, comprise a professional sensory panel, trained to quantify food attributes including appearance, aroma, flavor and texture. The group has more than 1,000 hours of experience in analyzing what they eat and drink and offer their services to the food industry.

Meullenet directs the Rheology and Sensory Program, a multidisciplinary program designed, in part, to provide basic information to the U.S. food industry to optimize food quality.

Companies who contact Meullenet’s program seek information on the quality of different aspects of their products. Products tested at in the sensory laboratory include cheese, yogurt, hot dogs, meats, baked beans, poultry, tortilla chips and rice.

The sensory panelists can evaluate the bouquet of a red wine, the crispiness of a tortilla chip, the taste of rice or the appearance of a fried chicken. They do so by using certain words to describe different aspects of the food or beverage set before them, each one building up a vocabulary to create a 200-word description.

Meullenet and other researchers then combine words that overlap to build a lexicon to describe a particular product.

While the panelists eat, Meullenet and his graduate students strive to develop instrumental methods of predicting consumer acceptance of products. Although they can evaluate aroma, taste and appearance, for their own research purposes they focus primarily on texture. Most people have used the descriptive words springy, tough, chewy, hard and crisp to describe the texture of food. In the laboratory, Meullenet looks at cohesiveness, the amount the sample deforms; denseness, the compactness of a cross section of the sample; and fibrousness, the amount of grinding of fibers required to chew through the sample.

"We break texture down into many attributes," Meullenet said.

Take your average tortilla chip, for example. Meullenet uses a machine to apply a force to the chip and crush it, much like a person’s teeth would. He varies the force and studies the resulting fracture patterns. He can do this using a simple press or with replicas of the sensory panelists’ teeth, designed to give the researchers some realistically shaped tools to work with.

Using these and other tests, he tries to relate the sensory panel’s perceptions to the instrumental measurements.

"We’re trying to find out what’s happening with the physiology of perception," he said. "We want to understand what people do when they chew."

Although many scientists have studied aspects of taste, few have looked at the mechanics of eating. For a long time, researchers believed that chewing was a rhythmic ritual unrelated to the perception of food and drink. But studies have shown that if you numb certain facial muscles, the brain perceives food differently.

Eating at the sensory laboratory is not always a picnic: Meullenet has modified a machine, commonly used in dentist’s offices to evaluate jaw problems, for use in measuring chewing speeds. The "machine" consists of a headset with giant ear pads connected to a series of electrodes placed at strategic locations on the face, and these connect to a laptop computer. A magnet is placed under the person’s front lower teeth. Meullenet uses electromyography to measure the muscle activity during chewing.

He has discovered that chewing speeds vary greatly among individuals, even when they have been instructed to chew at a certain rate. When asked to eat at one chew per second, the sensory panelists ranged from one chew every two seconds to one chew every half a second. Meullenet has demonstrated instrumentally that food breaks down differently at different speeds.

"We are now investigating the importance of velocity in perception," Meullenet said.

He also incorporates advanced modeling techniques, including Artificial Neural Networks and Fuzzy Logic, to predict food texture from mechanical measurements.

Meullenet uses statistics to correct for consumer bias. Consumers show reluctance to pan a product, even when the researchers tell them there’s no wrong answer.

"When you eat something at home or at a restaurant you’re a lot more relaxed," he said. "Here people won’t say 'it tastes terrible.’"

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