Intensity
The substances that give chili peppers their intensity when ingested or applied topically are capsaicin (8-methyl-N-vanillyl-6-nonenamide) and several related chemicals, collectively called capsaicinoids. Capsaicin is the primary ingredient in the pepper spray used as an irritant weapon.
When consumed, capsaicinoids bind with pain receptors in the mouth and throat that are responsible for sensing heat. Once activated by the capsaicinoids, these receptors send a message to the brain that the person has consumed something hot. The brain responds to the burning sensation by raising the heart rate, increasing perspiration and release of endorphins. A 2008 study reports that capsaicin alters how the body's cells use energy produced by hydrolysis of ATP. In the normal hydrolysis the SERCA protein uses this energy to move calcium ions into the sarcoplasmic reticulum. When capsaicin is present, it alters the conformation of the SERCA, and thus reduces the ion movement; as a result the ATP energy (which would have been used to pump the ions) is instead released as thermal energy.
The "heat" of chili peppers was historically measured in Scoville heat units (SHU), which is the amount of chili extract added to sugar syrup before its heat becomes detectable to a panel of tasters. Bell peppers rank at 0 SHU, New Mexico green chilis at about 1,500 SHU, jalapeños at 2,500–5,000 SHU, and habaneros at 300,000 SHU. The modern commonplace method for quantitative analysis of SHU rating uses high-performance liquid chromatography to directly measure the capsaicinoid content of a chili pepper variety. Pure capsaicin is a hydrophobic, colorless, odorless, and crystalline-to-waxy solid at room temperature, and measures 16,000,000 SHU.
Read more about this topic: Chili Pepper
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