The heat in chillies is caused by a group of chemicals called capcaicinoids. These chemicals are found only in the fruit, and the more concentrated they are, the hotter the chilli is. Their concentration is affected mostly by the choice of variety, though levels are also influenced by growing conditions, sun, soil and age of the fruit.
The degree of heat is expressed in Scoville Heat Units (SHU), named after Wilbur Scoville, an American pharmacologist who devised a taste test for measuring chilli heat in 1912.
The scale starts at zero for sweet peppers, which have no heat, and increases up to the current record holders – varieties of C. chinense from Bangladesh, Northeast India and the Caribbean – which reach heat levels of 1,000,000 SHU or more.
|SCOVILLE HEAT SCALE|
|Ghost Pepper, Bhut Jolokia||855,000 – 1,040,000||208 times hotter than Jalapeno|
|Habanero – Red Sativa||350,000 – 577,000||115 times hotter than Jalapeno|
|Chocolate Habanero||300,000 – 500,000||100 times hotter than Jalapeno|
|Thai Chile Duo||50,000 – 100,000||20 times hotter than Jalapeno|
|Thai Hot, Red||50,000 – 100,000||20 times hotter than Jalapeno|
|Tabasco pepper||30,000 – 50,000||10 times hotter than Jalapeno|
|Long Red Cayenne||30,000 – 50,000||10 times hotter than Jalapeno|
|Serrrano||10,000 – 23,000||4 ½ times hotter than Jalapeno|
|Jalapeno||2,500 – 8,000|
|Pasilla Bajio||1000 – 2000||40% the heat of a Jalapeno|