Though there are only a few commonly used species, there are many cultivars and methods of preparing chili peppers that have different names for culinary use. Green and red bell peppers, for example, are the same cultivar of C. annuum, immature peppers being green. In the same species are the jalapeƱo, the poblano (which when dried is referred to as ancho), New Mexico (which is also known as chile colorado), Anaheim, serrano, and other cultivars.
Peppers are commonly broken down into three groupings: bell peppers, sweet peppers, and hot peppers. Most popular pepper varieties are seen as falling into one of these categories or as a cross between them.
The habanero chili pepper is known for its unique combination of intense flavor, aroma and heat
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.[14][15] Capsaicin is also the primary component in pepper spray, a non-lethal 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[16] 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.
A display of hot peppers and a board explaining the Scoville scale at a Houston, Texas, grocery store
The "heat" of chili peppers was historically measured in Scoville heat units (SHU), which is a measure of the dilution of an amount of chili extract added to sugar syrup before its heat becomes detectable to a panel of tasters; the more it has to be diluted to be undetectable, the more powerful the variety and therefore the higher the rating.[18] 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.