© 2018 by Janelle E. Letzen, PhD

 
Taste
What are taste buds?
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What do you call flavor's best friend? A taste bud! 😬😬😬 Terrible jokes aside, taste buds really do a lot of the initial heavy lifting when it comes to gustation, or taste. These little guys are mostly found within the bumps, or papillae, on your tongue, but can also be found in the cheeks, soft palate, and throat.

 

Each taste bud has both gustatory (shown as mango) and stem cells (shown as avocado). About every 10 days, stem cells replace old gustatory cells with new ones. So if you burn your tongue with something really hot, no worries, you'll have a new set of gustatory cells within about a week.

When combined with our senses of smell, touch, and sight, we can perceive countless flavors stemming from at least 5 basic tastes: sweet, sour, salty, bitter, umami.

Sushi Science | Janelle Letzen | Taste
What are tastants and how do they lead to taste?

When we chew or drink something, tiny molecules, called "tastants," are released from the food/drink and mix in with our saliva. Tastants then bind to receptors on taste bud gustatory cells. 

This binding triggers an action potential that passes sensory information along to our brain for complex perception, combining reward, emotion, memory, and cognitive processes. Each tastant uniquely triggers action potentials. For example, salty tastants open sodium channels, but sour tastants seem to open proton channels. 

Are there other tastes aside from salty, sweet, sour, bitter, and umami?

It seems like it! Recent research suggests that there might be gustatory cells for additional tastes, like "fatty," "alkaline," "metallic," and "water-like" flavors. So far, there is promising evidence for fatty-specific gustatory cells.

 

A lot of people think that "spiciness" of foods is a taste. Actually, though, it is not a taste. Instead, the molecule capsaicin (found in foods like peppers) acts on pain receptors, so is processed by pain/pleasure brain pathways.

Are there zones on your tongue for specific tastes?

A common misbelief (still found in some textbooks!) is that certain tastes are restricted to specific tongue zones. All tastes are sensed in all parts of the tongue. Bitter tastes are a slight exception because they actually are more sensitively detected in the back of the tongue.

References

[1] Beidler, L. M., & Smallman, R. L. (1965). Renewal of cells within taste buds. The Journal of cell biology, 27(2), 263-272.
[2] Chaudhari, N., Yang, H., Lamp, C., Delay, E., Cartford, C., Than, T., & Roper, S. (1996). The taste of monosodium glutamate: membrane receptors in taste buds. Journal of Neuroscience, 16(12), 3817-3826.

[3] Chandrashekar, J., Hoon, M. A., Ryba, N. J., & Zuker, C. S. (2006). The receptors and cells for mammalian taste. Nature, 444(7117), 288.

[4] Fukunaga, A., Uematsu, H., & Sugimoto, K. (2005). Influences of aging on taste perception and oral somatic sensation. The Journals of Gerontology Series A: Biological Sciences and Medical Sciences, 60(1), 109-113.

[5] Mattes, R. D. (2009). Is there a fatty acid taste?. Annual review of nutrition, 29, 305-327.