2 Comments »Posted on Tuesday 2 September 2008 at 3:02 pm by Jacob Aron
In Chemistry

Everyone enjoys a good curry. I actually can’t think of anyone I know who doesn’t. I’m not a sadistic hotter-than-the-sun curry lover, more of a korma/tikka masala kind of guy, but there’s something about spicy food that really gets the taste buds going.

That something is a molecule called capsaicin (pronounced “cap-say-sin”) which is found in all varieties of chilli peppers. Capsaicin is hydrophobic, meaning that it repels water molecules – which means drinking water won’t cool your burning tongue after a mouthful of too-hot chilli, but if cold enough it might numb your mouth for a bit.

I cook a lot, and I’ve learnt to treat raw chillies more like radioactive waste than a tasty ingredient. My worst experience with capsaicin came when I decided to take a shower after preparing a curry. I didn’t know that I still had juice from the chilli (and thus capsaicin) on my fingers and the act of showering spread the substance all over my face and hands because the capsaicin does not dissolve in water. I began to realise this only once my skin started burning. In the end, I don’t think I got to sleep until the early hours of the morning thanks to the pain!

There was only one thing that provided any relief. Capsaicin will bind to fat molecules, so bathing your hands in a fatty substance can help to stem the pain – this is also why Indian meals are often served with an accompaniment of raita, a yoghurt based dish. My flatmate was amused to watch me cover my aching hands with anything I could find in the kitchen that contained fat – I tried butter, oil, and finally milk which worked best. I cursed myself for being a semi-skimmed drinker, rather than the full-fat variety!

At least the chillies I had used weren’t that strong, relatively speaking. The “heat” of a chilli is measured on a scale named after its creator, Wilbur Scoville. The more Scoville heat units (SHU) a chilli has, the deadlier it is! Pure capsaicin has a Scoville rating of 15 to 16 million SHU, whereas chillies you would normally buy in a supermarket are rated around 2500 SHU. Some hot sauce manufacturers even proudly display their Scoville rating on the packaging – check out this 600,000 SHU sauce!

Scoville’s original method for rating chillies was actually pretty unscientific. Known as the Scoville Organoleptic Test, it requires an extract of the chilli to be mixed with a water and sugar solution. This concoction is then given to a panel (normally of five people) to taste. If three out of the five agree they do not detect any heat from the chilli, then the ratio of dilution is the SHU rating. For example, if a certain chilli must be diluted with one part extract to 100 parts water and sugar, then it has a rating of 100 SHU.

This subjective test has since been replaced with a machine – known as a high performance liquid chromatograph – which can measure the capsaicin in a chilli. This measure can then be converted back to the Scoville units for comparison, although industry consensus is the modern technique yields a Scoville rating about 20-40% lower than the original method.

So, the next time you tuck into a tasty curry, whether it be a mild korma or a deadly phall, remember capsaicin, watch out for the Scoville rating, and always have a glass of full-fat milk on hand!


  1. 2 Comments

  2. Yes, milk is definitely the antidote to chilli in the eyes or worse…chilli willy. If you ever get pepper sprayed or teargased even, a bottle of milk emptied into your eyes will help. Messy, but effective. It probably works with lacramation caused by cut onions too, but I’d need confirmation of that.

    Incidentally, is there not some hydrolysis processing taking place, rather than it simply being capsaicin dissolving in the fat? That would explain why butter didn’t work. Lactic acid and all that in the milk.

    By David Bradley on Tuesday 2 September, 2008 at 6:05 pm

  3. I’ve only ever read that capsaicin is dissolved in fat. Do you know what the hydrolysis taking place involves?

    By Jacob Aron on Tuesday 2 September, 2008 at 6:29 pm

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