The heat in a chilli comes from a family of chemicals known as capsaicinoids, most commonly capsaicin and dihydrocapsaicin, but also nordihydrocapsaicin, norcapsaicin, homocapsaicin, nornorcapsaicin, and homodihydrocapsaicin,

The original Scoville Organoleptic Test measured the heat level of a chilli by using five human subjects to taste a chilli and record the heat level the capsicanoids caused them to feel.

The test procedure is as follows.

  • An alcoholic extract of the chilli to be tested is made.
  • A level of extract such that a negative response will be obtained is chosen and diluted with 5% sucrose solution to make a 50ml sample.
  • This initial level of extract is increased and the solution remade until three out of five tasters report a burning sensation. Between each iteration the testers should wash their mouths out with water, and wait for five minutes.
These days chilli heat is measured in a slightly more accurate manner, using high-performance liquid chromatography (HPLC) to measure the number of capsaicinoids present in a sample.

Test method taken from the Zarc International website at