WHY SPICY FOOD TASTE SO HOT WHILE MINT TASTE SO COLD?

This is a question which pops every time when we eat anything spicy. When we eat anything spicy, we immediately feel a burning sensation in our tongue. Tears start pouring out from our eyes if it too spicy. But why? Why is it so? Does our body does not like spicy food? Well, let us understand it with science. There is a family of protein sensors which is present in tongue. It detects hot or cold things. The chemicals present in the spicy food triggers these proteins and they (the proteins) think that the tongue is in fire and send signals to brain. Hence, we think that our tongue is in fire when we eat spicy food. There are a lot protein sensors in our body. They are mainly found in skin and tongue. The sensor which detects temperature is TRP-channel protein. For example - TRP-A1 detects temperature from 10-15 degree Celsius while TRP-V1 sense temperature from 40-45 degree Celsius. Now, 10-15 degree Celsius range is too cold to burn us. So, when TRP-A1 sends signal to the brain, the brain does not activate the something-is-burning sensation. But when TRP-V1 sends it signal, it immediately activates the something-is-burning sensation and we react accordingly, like pull our hand from the fire. Similarly is the case when we talk about tongue. When we eat something not-very-spicy, we munch happily and don't feel the burning sensation. But when we eat something really spicy, like Habareno, we tend to call the fire engine.

Now lets proceed to the mint. Mint does the very same thing. Instead it activates cold relatives of TRP family, which sense the cold temperature. So, when we pop a mint into our mouth, the mint activates the TRP family and they (TRP family) sends signal to the brain that something cold is kept in our tongue. As there were many relatives which determined the heat, there are a lot of TRP relatives which determine the coldness. According to the protein sensor which sends the signal, the brain reacts. 

As it is very important to know how spicy the food is, a unit called 'Scoville units' has been introduced which determines the spiciness of a food. So, do ask for the Scoville measurement of an unknown food before you eat!