A new study could explain why people register some flavors faster than others, possibly because of the molecular size of each flavor. The study also provided an explanation for why people register taste faster when food or drink moves more quickly on their tongue than when they are held steadily in their mouth. The findings indicate that both the speed at which food and drink move in our mouths and the size of the molecules in the food we consume affect our sense of taste.
“Our tongues have papillae that behave like a sea of kelp in an ocean,” said Kai Zhao, the paper's lead author and associate professor of otolaryngology at Ohio State University College of Medicine. “Those papillae – the little bumps that contain taste buds on the human tongue – move and wave as food or drink flows past them.”
The human tongue has four types of papillae; three of them contain taste buds. (The fourth kind is the most common on the tongue and mainly serves as a way to increase friction.)
For this study, the researchers modeled the way flavors move around the papillae in the tongue, using a range of salty and sweet stimuli. The researchers also built a computer model that simulated previous studies on taste perception.
The model considered the human tongue as a porous surface, with the spaces between the papillae acting like the holes of a sponge. Then the researchers simulated what would happen if they let a series of salty and sweet flavors across that surface, first quickly, in an intense rush, then slowly. They found that the rapid transmission of flavors across the tongue caused the flavors to penetrate the pores of the papilla more quickly, and that would register the taste more quickly.
And their findings could explain why taste buds registered a sweet compound with a small molecular size more quickly compared to those with a large molecular size, such as salty flavors.
“Smaller molecules can diffuse more quickly, and we think this may be why they pass through the papilla's holes faster,” said Zhao.
This study focused on the early stages of taste — what happens before taste buds have even registered a taste. Compared to the other senses – image and sound, for example – taste works with a kind of time delay. We hear a sound almost as soon as it is broadcast; it takes a little longer for our taste buds to register.
"That early response depends on how the molecules of what we consume interact with the surface of the tongue," Zhao said. “It is a complex process.”
Prior to this study, scientists knew that if they dropped a flavored solution on a person's tongue, the intensity of that solution's taste would increase over time. But they didn't know why that happened.
Zhao said scientists assumed the increase in taste had something to do with papillae, so for this study his lab focused on studying the mechanics of how papillae work.
“Our taste buds are important,” he said. “They help us figure out what foods to eat, how much food to eat, and how to balance the body's nutritional needs with its energy needs.”
Taste buds also help people avoid toxins, can help identify edible and nutritious foods, and contribute to people's cravings for things like ice cream and chips.
