The study conducted by Fabian Grabenhorst and his colleagues at Oxford University reveals that the brain’s response to fatty food is not just due to its taste, but also its mouthfeel. In their research, the team found that the orbitofrontal cortex, which is responsible for sensations and the attractiveness of food, becomes excited when recognizing fatty foods. Fat increases the viscosity of liquid foods, making them feel richer in our mouths. However, the researchers were more interested in the melting oiliness of fatty foods, as it reduces friction when sliding against the tongue and walls of the mouth.
To test this theory, the team prepared vanilla-flavored milkshakes with varying fat and sugar content. They also obtained pig tongues from a local butcher to measure the sliding friction of these milkshakes in conditions similar to those found in human mouths. The results showed that friction decreased as fat content increased.
The team then recruited more than twenty test subjects who slurped on milkshakes and were asked to rate how much they would be willing to pay for more shakes after tasting them. Brain imaging was used during this process using functional magnetic resonance imaging (fMRI) technology. The results showed that differences in composition between shakes and their pleasantness were reflected in reactions of the orbitofrontal cortex.
The preference for certain flavors was partly explained by mouthfeel associated with sliding friction during consumption. Mouthfeel plays an important role in food choices as well, as confirmed by another part of the experiment where test subjects were given three curries with different fat content and asked to choose their favorite for lunch without knowing they were being observed by researchers. Results showed that those whose orbitofrontal cortex reacted strongly to greasy mouthfeel during shake testing had piled up plates of fattier curries for lunch.
Grabenhorst said that these findings may help develop low-calorie foods that still provide consumers with a satisfying mouthfeel experience without sacrificing taste or nutritional value. The study was published in The Journal of Neuroscience journal, shedding light on how our brains make decisions about what we eat based on factors beyond just taste alone.