Capsaicin is the naturally occurring chemical in chile peppers. It provides the kick that fires up chili, salsas, barbecue sauces and other spicy culinary endeavors. While most peppers contain this element, different varieties contain different severities of heat. A cook has to learn how to choose and use peppers based on their capsaicin content.
Found in nearly every member of the genus Capsicum, capsaicin may have evolved as a natural defense so critters would not eat them into oblivion. Most of the peppers, commonly referred to as chili peppers, contain at least trace amounts of capsaicin. The common bell pepper is the only member of the Capsicum family that contains little or no capsaicin, which accounts for its sweet, mild and decidedly cool taste. As of May, 2011 the hottest chili pepper on record is the Bhut Jolokia, or "Ghost Pepper."
The Scoville Scale
In the early 1900s, Wilbur Scoville began experimenting with capsaicin and devised a heat scale to rate chili peppers. Pure capsaicin tops the scale with 15 to 16 million units. The aforementioned ghost pepper comes in at about 1 million units. Cooks looking to add considerable fire to their foods may start with jalapenos at around 2,500 units and then move up the scale with the serrano or chipotle, which rate between 10,000 and 23,000 units. Tabasco peppers are next at around 30,000. Habaneros or Scotch bonnets rate between 100,000 and 350,000 units.
The jalapeno and habanero peppers are household names, but many more capsaicin-heavy peppers exist. The pequin, guajillo, chiltepin, datil and aji peppers offer a range of choices from the pepper family for those who appreciate experimentation. Large, milder peppers such as the anaheim and poblano make good stuffing shells for appetizers or main dishes. Hotter peppers need to be used cautiously as their heat content will spread throughout the dish.
The capsaicin oils contained in pepper can be irritating if they get near your eyes or nose. Wear latex gloves when cutting chili peppers. For extra precaution, thoroughly wash your hands, and the cutting area, with warm, soapy water when you're finished with the preparation. If the heat becomes overwhelming during the meal, don't try to quench it with water. Water will not have much of a cooling effect against the oil-based capsaicin heat. Keep a dairy product on hand, such as a glass of milk, to counter the heat of the capsaicin.