You have probably had the burning sensation of eating a hot jalapeno or other tear-inducing pepper. What causes this painful fire in your mouth?
The short answer is capsaicin. But what exactly is capsaicin? How does it work? Why do people drink milk and not water to relieve the pain? Reactions has the chemistry to answer all of these sizzling questions.
Milk, however, contains casein, a fat-loving compound that binds with spicy capsaicin oil and then washes it away.
Chilli heat is measured using Scoville heat units (SHU), which is an inexact measure of capsaicinoid concentration.