How are the hottest chilis determined? Believe it or not, the most common test involves human taste-testers. In the “Scoville Organoleptic Test”, chili extract is diluted in sugar water until the heat of its spice is no longer detectable to a panel of tasters. The resulting heat rating, measured in Scoville heat units, is a measure of how much the chili had to be diluted. “The hottest chiles, such as habaneros, have a rating of 300,000 or more, indicating that their extract has to be diluted 300,000-fold before the capsaicin present is undetectable.” [wikipedia]

Here’s a list of the hottest ten chilis on the Scoville scale:

1. Naga Jolokia (855,000 - 1,041,427 SHU): Also called Bhut Jolokia (’ghost pepper’), this hybrid from India’s easter Assam region recently tested as the most potent chili in the world.
2. Dorset Naga (876,000 - 970,000 SHU): a relative of the Scotch Bonnet (see below), this exceptionally hot chili is named for its British county of origin.
3. Red Savina (350,000 - 577,000 SHU): This former world record holder is still claimed by some to be the world’s hottest chili. It is a variety of…
4. Habanero chile (100,000 - 350,000 SHU): Habaneros extract is used in Dave’s Insanity Sauce.
5. Scotch Bonnet (100,000 - 350,000 SHU): The name refers to the chili’s resemblance to a Tam o’shanter.
6. Jamaican Hot Pepper (100,000 - 200,000 SHU): As its name suggests, this variety hails from sunny Jamaica
7. Thai pepper (50,000 - 100,000 SHU): A variety of these grows Sydney’s Circular Quay public gardens. It is a source of late-night entertainment for drinkers, who add them to their hamburgers or eat them as a dare.
8. Malagueta pepper (50,000 - 100,000 SHU): A popular chili within Brazil, to the extent that ‘malagueta’ is synonymous with ‘hot peppers’ in Portuguese.
9. Chiltepin pepper (50,000 - 100,000 SHU): According to Wikipedia, this wild pepper is perhaps the ancestor of all modern chilis.
10. Cayenne pepper (40,000 - 90,000 SHU): This common pepper has been used for centuries as a digestive stimulant.

(source: wikipedia)

And in case you were wondering, the active ingredient in chilis is capsaicin, which stimulates a heat-sensitive pain receptor. It’s also the ingredient that gives police capsicum spray, or ‘pepper spray’, its kick: at up to 5 million SHU, there’s little wonder that being sprayed with this stuff is one of the worst kinds of pain imaginable. Even Marines hate it.