Science class explores the matter of taste

by Sonia Fernandez

Flavor is in the brain, and nowhere is that clearer than in neuroscientist Matthieu Louis’s introductory neurogastronomy class. The course, “Unraveling the Science of Flavor: From Genetics and Data to Michelin Stars,” part of the campus’s undergraduate Discovery Seminar series, unpacks the multimodal phenomenon we call taste. 

“Food perception is a wonderful way to introduce concepts of biochemistry and neuroscience through our own sensory experience,” Louis says. “Our mouth is a magnificent multisensory laboratory.” 

In this class, students are both experimentalists and experimental subjects as lectures are augmented with interactive demonstrations designed to highlight how multiple sensory pathways meet to create flavor. There are the ones we’re most familiar with, such as the five basic tastes detected on our tongues, as well as the surprisingly dominant role of smell in constructing flavor. Lesser known perhaps, but no less significant, are the roles of texture, vision and sound, and the expectations they build during food presentation. 

“This integration is not redundant; it is a survival mechanism: Animals evaluate food along multiple dimensions simultaneously to make better choices about what to ingest,” Louis says. Humans subsequently elevated this ability to sense complex flavors by creating cuisine, he adds. 

Throughout the quarter, students gain insights into the cellular and molecular underpinnings of these sensory pathways while learning to appreciate the individual differences in how humans interpret flavors. Some might discover that they are “supertasters,” with higher-than-normal numbers of taste buds on their tongues. Others might find they have genetic variants causing them to respond differently to bitter substances or specific odors. 

“I was born without a sense of smell,” says student Alisa Moyse. “I took this class because I wanted to get a better idea of what that means in my life compared to others and how I perceive taste.” What fine-tuning of flavor her classmates lost during the jellybean test — one in which the participants had to block airflow through the nose while eating a jellybean — is a typical situation for Moyse, who has learned to lean on other aspects of flavor perception such as texture and mouthfeel. Fortunately, it turns out, she also has more taste buds than usual. 

The class was also revelatory for Claire Corman, who, like Moyse, realized the importance of retronasal olfaction — the smell sensations that reach odorant receptors throughout the air passage in the back of the mouth while eating. “We learned a lot of the chemistry and biochemistry behind our taste buds,” she says, “and I learned why I’m a picky eater and why some people like certain foods more than others.” 

The class also features occasional guest experts in flavor, such as Pierre Henry and Nelly Mousseau. The husband-and-wife team behind popular Montecito bakery and café Bree’osh, they are known for their artisanal breads and pastries. The pair brought panettone to demonstrate the varying levels of complexity and texture in flavor yielded in the process of making the iconic Italian yeast cake. The students sampled three variations on the panettone theme, learning about the effects of fermentation and temperature on the final result, and the bakers received feedback through sensory evaluations that drew on the flavor vocabulary and perceptual skills that students had been building throughout the quarter.

The class grew from Louis’s interactions with chefs earlier in his career, when his lab was in Barcelona. “I realized that the empirical knowledge of chefs can be used as a starting point for new experiments,” he says. It gained steam during the pandemic, when quarantines required all UCSB instruction to move online, and he had to find experiments students could run at home. Since then, the course has continued to evolve each quarter by incorporating ever more complex experiments.

Whether it opens the door to future science careers, awakens a love for gastronomy or both, Louis hopes the class makes dry concepts of biochemistry less abstract.

“Showing students that neuroscience is still driven by a near-infinite number of open questions is exciting,” he says, “because it reveals how much room there is for a new generation of bright minds to engage in research.”