Why Peppers Taste Hot

The heat sensation is caused by capsaicin, which is a colorless, odorless, oily chemical found in peppers.  Capsaicin binds with certain sensory neurons which then more or less trick your body into thinking that it is being burned or at least experiencing excessive amounts of heat in the area that the capsaicin comes in contact with, even though no actual physical burning is taking place.

(Warning, Extreme Nerdery Ahead) Specifically, what is going on is that the capsaicin is binding to the vanilloid receptor (VR1), which is a member of the superfamily TRP ion channel and thus is referred to as TRPV1;  by binding to the VR1 receptor, the capsaicin molecule will produce the same sensation, or signal to the brain, that normal heat will produce when activating the TRP receptors.  This is why eating peppers makes your mouth feel really hot, even though it’s not. (End Extreme Nerdery). 

Interestingly, in extreme cases where exposure to capsaicin is high, such as in pure capsaicin extract, the sensation can be so “hot” that the body will be tricked into inflaming itself; so it would appear as if you are actually burned, even though the capsaicin doesn’t actually burn you at all, just tricks your brain into thinking it’s being burned. (Queue Matrix: Your mind makes it real.)

Capsaicin is not just a substance that makes your food extra tasty, it is also used in “pepper spray”, hence the name.  Anytime relatively undiluted capsaicin comes in contact with your skin, particularly your eyes or breathed into your lungs, it will cause you to feel like you are being burned, even though you aren’t.  So it makes a very effective deterrent without actually causing any real damage to the person being sprayed; or rather I should say causes no real damage if it’s not too strong a level of capsaicin as noted later.

There is even a scale for measuring hotness as a function of a chili pepper, the “Scoville Organoleptic Test”. This scale was developed by chemist Wilbur Scoville.  The hotness is measured in multiples of 100 units, referring to how much sugar-water was needed to dilute the pepper to the point where your brain is no longer tricked into thinking you are being burned.