Research at Monell is helping to reveal how humans recognize, perceive and respond to tastes, odors and other chemosensory stimuli, such as carbonation, menthol and capsaicin. Many studies focus on individual differences, examining how factors such as genetics, age, gender, experience, and the environment influence sensory capabilities. Scientists are also exploring how interactions within and between the senses influence perception of chemosensory stimuli.

Much of the research at Monell explores the role the chemical senses play in our sensory world. Although tastes, odors, and chemical irritants are rich sources of stimulation throughout our lives, understanding of these complex systems is still unfolding. Monell’s sensory research program focuses on learning more about how we detect and perceive these stimuli and how those processes impact us across our lifespan.

It has long been established that our sense of taste detects four basic sensations – sweet, salty, sour, and bitter. More recently, increasing consensus has developed for the addition of a fifth class of taste sensation: umami. Sometimes described as “savory,” “brothy,” or “meaty,” the sensation of umami is conveyed by several substances, including the amino acid glutamate. Glutamate is found naturally in many foods, including fish, cheese, tomatoes, peas, corn, and human milk, and as monosodium glutamate, is often used to enhance the flavor of food.

These five sensations are the foundation for many of the research projects conducted at Monell. Scientists at the Center are exploring not only fundamental issues such as how we detect each of these sensations and how that information is transmitted to the brain, but also more complex issues such as the genetics of individual differences in taste perception, taste suppression and enhancement in mixtures, subcategories of tastes (for example, is there more than one type of bitter or sweet taste?), and taste localization within the oral cavity.

No one knows exactly how many compounds can stimulate the olfactory system, but it is clear that the number is very large. A single compound may result in a different sensation for one person than another, and it is not uncommon for an individual to experience distinctly different odor qualities when the same compound is presented at various levels of concentration. Throughout our lives, the olfactory system is sending a nearly constant stream of information to the brain. The brain processes this information and organizes it into a coherent whole. Monell’s scientists investigate olfaction at all levels– from the influence of molecular structure of compounds on their perceived odor to the relationships among odor perception, emotion, and memory.

Chemosensory irritation is the detection of chemical irritants in the mouth and nose, or on the skin. This sensory system is anatomically independent from the senses of taste and smell. The detection of chemosensory irritation can also serve as a warning sign for a variety of potentially harmful stimuli. However, sensations of irritation — such as pungency, warmth, cooling, and tingle — are sometimes considered desirable in certain foods, beverages, and health-care products. Researchers at the Center are exploring the factors that influence how individuals perceive and respond to chemosensory irritants, and how different irritants interact.

Tastes, smells and chemosensory irritants are often perceived as mixtures in food or beverages. A common example is the burning that is often experienced when eating spicy foods. In this case, the trigeminal nerve carries sensory information about chemosensory irritation detected in the mouth and throat, while other nerves carry information about tastes and odors detected in other parts of the mouth and the nose. All of these sensations are combined in the brain to produce what is often mistakenly referred to as the ‘taste’ of a particular food. In fact, the combined sensations make up ‘flavor,’ which includes not only tastes, but also odors along with chemosensory irritation. Naturally the interaction of taste, smell, and chemosensory irritation is a topic of considerable research interest at the Center.

Ongoing research projects at the Center that are expanding knowledge of chemosensory sensation and perception include:

• Identification of “blockers” of specific tastes, smells, and irritants, such as bitter tastes, food odors, or painful irritants
• The study of interactions among taste, smell, and chemosensory irritation
• The roles played by age, gender, prior dietary experience, and genetics in the development of human taste preferences and sensitivity
• The influence of cognitive factors in our responses to odors and irritants
• Investigation of the relationships among odors, memory, and emotion
• Analyses of how individual taste qualities interact to enhance or suppress taste perception
• The relationship between sensitivities to bitter and sweet tastes and alcohol intake
• Identification of individual differences in perception of different bitter compounds
• The roles played by age and gender in determining preference for various concentrations of carbonation in beverages