Why do people grimace when tasting sour things?

Try this: Take a lemon, peel it and eat it but don't frown. You can do it? No, maybe not. How does a fist-sized lemon have the power to make your face move against your will?

Scientists have not explained this yet, but it is possible that the answer involves three things: protons, vitamin C and tropical fruits that our ancestors ate when they lived on trees.

The flavor that we call "sour" has a direct relationship with acidity. Chemically, the sour taste is when your taste buds say "there's lots of liquid protons in your mouth right now!" Of course, protons are not really sour. Research shows that our agencies have evolved to explain the attributes that are sour.

The face that grimaced when eating sour was a kind of rejection.

To survive, humans need to eat ascorbic acid , also known as vitamin C. This is necessary to keep many of our cells and tissues working normally. If not enough, people can get scurvy (a disease caused by vitamin C deficiency), a disease that can be fatal.

Unfortunately, most organisms can make their own vitamin C, but we don't. According to a 2011 study in Genetica magazine, about 61 million years ago, genes coding for vitamin C synthesis in mammals were mutated. Later, we had easy access to dietary vitamin C to the point where mutations did not occur.

"People have lost the ability to make their own vitamin C because we have absorbed it a lot from fruits , " said Paul Breslin, professor of Nutrition Science at Rutgers University in New Jersey.

Modern people really like the sour taste in the right context. In fruits such as apples and oranges, sweet and sour flavors create balance and make us consume vitamin C. In terms of salty, sour taste can indicate fermentation, already during the journey. human chemistry.

If food is delicious and good for humans, then why does lemon make us grimace?

"That grim face is a kind of refusal response , or a signaling response to ourselves and others , " Breslin said.

Scientists can guess what that signal might be, but they don't know for sure.

"Most of the fruits that we eat are not super sour. People won't naturally take the whole lemon out."

At least most people will not eat like that. But if they do, at least they won't get scurvy.