Mmmm…. Tastes good!

When you put something in your mouth tonight for dinner, a complex array of flavors may await you. You might not like all of the flavors, of course! But you can taste them, nonetheless. Have you ever wondered how?

Taste is a chemical sense. In that regard, it is similar to the sense of smell. Both taste and smell give us information about the chemical nature of our surroundings – taste giving us information about the chemical nature of what we’re about to eat, and smell giving us information about the chemical composition of the air we’re breathing. The senses of taste and smell are, in fact, closely related. Actually, the concept of flavor is really a combination of the taste, smell and texture of a substance. You’ve probably experienced how food tastes much more bland when you have a cold and can’t smell it. That’s because half of your ability to sense the flavor is lost when your nose is stuffy.

You might know that we have long believed to have only 4 basic taste sensations in our mouths -bitter, sweet, salty and sour. However, recent evidence seems to indicate that there may be 1 more thing we can taste – it’s called umami, or savoriness. Umami is the taste of non-salty flavorings like MSG. The combination of all 5 taste sensations provides the taste of any given substance. And these taste sensations are controlled by your tongue.

The tongue is a very rough, ridged surface, containing ridges and valleys called papillae. There are 4 types of papillae, 3 of which contain taste buds. Taste buds are onion-shaped groupings of 50 to 100 taste cells that protrude up into the surface of the papillae. When food is dissolved by the saliva in your mouth, it breaks up into different chemicals, which interact with different proteins on the surface of the taste cells. These proteins are called taste receptors.

The bitter taste receptors are a family of 30 or so related proteins called T2Rs (identified in 2000). Sweet taste receptors are combinations of T1R2 and T1R3 proteins, while umami is tasted by combinations of T1R1 and T1R3 proteins (all found in 2003). All of these proteins function in a similar manner. When triggered by their chemical, they change other proteins inside the cell, ultimately resulting in the transmission of a message of bitterness, sweetness or savoriness to the brain. Nothing passes in or out of the taste cells with these taste proteins.

There is currently only 1 candidate sour receptor protein, called PKD2L1 (discovered in 2006). This protein acts in a different way. Sour tastes are usually acidic, thus they contain hydrogen ions. These hydrogen ions block the channels for other ions (such as potassium). As a result, the ion concentrations in the taste cells change, which results in a sour signal being sent to the brain. While the salty receptor protein is currently unknown, it is believed that it probably allows sodium ions into the cell. This increase in sodium ions would result in the transmission of a salty signal to the brain. For all of these taste receptors, their underlying mechanism is the same – changing ion concentrations results in different taste signals being sent from the taste cells to the brain.

So now that these signals have been sent to the brain, the next challenge is for the brain to decode them. And here’s where we get to the real mystery of it. We don’t really understand how our brain interprets the signals that we get from our taste buds. In fact, the sensations of taste and smell are both really poorly understood at the levels of our brain. So unfortunately, I can’t tell you how that part works. Maybe someday we’ll have a better understanding of it!

Until then, all I can do is wish that you get to taste something you really enjoy today. (For me, that would definitely be chocolate…)