The Perception of Umami Taste in the Brain

Sensitivity to chemicals that stimulate taste and smell receptors, which are considered “chemical senses,” can be affected by several factors. Genetic inheritance, the degree of exposure individuals have to substances in their daily diet, and even the emotional and cognitive aspects that the food and/or substance represent for the individual, as well as the influence of advertising, are determining factors in the response to pleasure and the intensity that consuming such food will cause in the body.

To evaluate some of these factors, such as exposure to chemicals present in food, scientists conducted experiments with primates and humans, using salts of glutamate (monosodium glutamate—MSG) and inosinate (disodium inosinate—IMP) in aqueous solution, as well as foods that naturally contain them, such as cheese and tomatoes. They verified, through nuclear magnetic resonance, that neurons are capable of responding to these substances when placed on the tongue. However, they are even more responsive when umami substances are associated with harmonious aromas and/or a visual or emotional appeal, such as the smell of meat or cheese, or when offered with an attractive label such as “rich and delicious taste.” Furthermore, this appeal also activated two other regions of the cingulate cortex: the anterior pregenual and the ventral striatum, which also receive signals from the secondary cortex and are capable of receiving the sensation of pleasure and intensity of umami taste. Similarly, McCabe and Rolls (2007) also found that the combination of glutamate with a harmonious aroma is more pleasant than glutamate alone, indicating an interaction between the gustatory and olfactory components in the response to the interpretation of food sensations (GRABENHORST et al., 2008a; MCCABE & ROLLS, 2007).

CRICHLEY et al. (1996) used chocolate milk, tomato juice, and a test solution to analyze the degree of pleasure experienced by evaluators in situations of food deprivation and after a meal to determine “post-satiety.” They observed that there may be a direct correlation between the pleasure of food intake and activation of the orbitofrontal cortex. Therefore, this brain region plays an important role in representing the reward value of food stimuli such as chocolate, a sweet food, and the umami-rich food tomato. The pleasure caused by food may then also be generated by the secondary cortex.

Furthermore, GRABENHORST et al. (2008) also found that the state of deprivation can positively modulate the response to umami in the orbitofrontal cortex to make it pleasurable, so that, when satiated, the umami reward decreases, and the state of selective attention allows processing in different areas of the brain. When individuals are induced to pay attention to the pleasure of food or stimuli, they end up stimulating the secondary cortex and the pregenual cingulate cortex more. However, when they are attentive to the intensity of the stimulus caused by food, the primary cortex represents the greatest response (GRABENHORST et al., 2008b).

Therefore, umami taste can be thought of as a rich and delicious taste produced by the combination of the taste of glutamate and a harmonious pleasant aroma. This fact also allows us to understand the influence of other senses on the sensory analysis of umami taste, demonstrating its possible role in appetite and food intake control.