Although the term "chili" is generically applied to hot sauces, spices and peppers, not all chili plants produce hot peppers. The heat of a chili pepper is measured in Scoville units, based on a test developed by Wilbur Scoville in 1912. The test calculates the amount of capsaicin, the chemical that gives chilis their heat, that is contained in each variety of pepper. Chili peppers range in heat from zero to more that 2 million on the Scoville scale. Factors such as plant variety, weather, cross pollination and disease can all have an impact on the heat of chili peppers.
The heat level of the peppers produced by a chili plant depends on its variety. Chili peppers come in numerous sizes, shapes, flavors and levels of heat, including everything from meek sweet bell and banana peppers to scorching hot Scotch bonnets and habaneros. Much of the heat of a chili pepper is contained in its seeds and ribs. Remove and discard them to reduce the level of heat. When cooking with chili peppers, add ingredients that contain fats, acid or alcohol to help reduce the heat level.
Extreme changes in the weather, including the amount of rain received during the growing season, can alter the heat level of chili peppers. Plants that are stressed by drought or a long period of hot weather can produce peppers with more capsaicin and higher levels of heat. Conversely, a lot of rain or overwatering can reduce the heat of chili peppers by diluting the amount of capsaicin that they contain.
Plants that receive a generous amount fertilizer throughout the growing season will produce milder chili peppers than those that are only minimally fertilized. Continuing to provide fertilizer for the plant after it is fully grown and begins to flower allows it to grow larger chili peppers and generate a more plentiful harvest. Withholding fertilizer stresses the chili plant, causing it to conserve energy and thereby reducing the number of peppers it produces; the capsaicin concentrates in those few peppers, making them hotter.
Planting different varieties of chili plants too close together can result in cross pollination, altering the heat level of the fruit that is produced. Wind or insects carry pollen from a one type of pepper plant to another nearby variety. Contamination of hot chili pepper plants with pollen from plants that are lower on the Scoville scale can reduce the heat level of the peppers. Similarly, the fruit of plants that produce mild chilis may be impacted by cross pollination, increasing their heat. To prevent cross pollination, plant different varieties of chili peppers as far apart as possible.
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