We all know the feeling: you take a bite of a dish that’s a bit too spicy – and it feels like your mouth is on fire! The burning sensation is caused by capsaicin, a substance which fools pain receptors in your mouth into telling your brain that they are burning, even though there is of course no fire.

In 1912, the American pharmacist Wilbur Scoville (1865-1942) developed a scale for measuring the hotness of peppers. And get this: he did it by testing them himself.

He would grind up a piece of dried pepper and allow it to soak in pure alcohol overnight. He then gradually added the alcohol solution to sugared water, tasting all the time,

until he could feel ‘a weak, but clear prickling’ on his tongue. So he was effectively measuring how much the pepper had to be diluted before it could no longer be tasted.

Using this technique he invented the ‘Scoville scale’ which today goes from 0 (the ‘heat’ of a bell pepper) to 16,000,000 (pure capsaicin). Although the Scoville scale is still in use, no taste tests need to be carried out by humans:

today the concentration of capsaicin and related substances can be measured by laboratory machines.

The hottest pepper in the world so far is the Carolina Reaper. This red monster has a rating of 1,569,300 on the Scoville scale – at least 1500 times as hot as me. Ai, ai, ai!