The Scoville Scale & Capsaicin – What Are They?

When you encounter anything relating to chilli peppers, chances are you will probably see something relating to the Scoville Scale, Scoville Units or SHU.

If you’ve ever wondered on what this is or how it is measured, you’re in the right place!

The method for measuring Scoville Units was first devised in 1912 by Wilbur Scoville with the Scoville Organoleptic Test.

What the scale measures is the levels of capsaicin in the peppers that are being tested. It is unfortunately a subjective measurement dependent on the sensitivity of the testers, so is not a very precise way to measure the capsaicinoid concentration, but it does give us a pretty good idea just how hot it will roughly be.

Capsaicin is an active component of chilli peppers and is effectively an irritant for us humans and other mammals. If you’ve ever eaten a chilli or something spicy and felt a burning sensation, that will be the capsaicin from the pepper kicking in.

So how is the level of capsaicin measured?

Scoville’s method involved dissolving an exact amount of dried pepper in alcohol to extract the capsaicinoids from the peppers. This is then diluted in sugar water and given to a panel of 5 trained testers in decreasing concentrations. Once a majority of the testers (3 or more) can no longer detect any sort of heat element from the solution, this then determines the heat level.

In other words, how many times do you have to dilute the capsaicinoids before they become undetectable, the higher the concentration of sugar water, the hotter the pepper.

As we’ve already mentioned, this test is all dependent on the testing panel. There are however other things which can skew the results further. Things like sensory fatigue also come into play. Sensory fatigue is where the human palate desensitizes to capsaicin after a while and is therefore only good for a few test samples before this starts to really kick in. Because of this it means results can often vary, some by as much as 50% give or take.

Given technological advancements of the modern era, there are now newer ways to measure the pungency of peppers, such as the method devised by the American Spice Trade Association (ASTA). This involves a method using high-performance liquid chromatography (HPLC) which identifies and measures the concentration of the peppers heat producing chemicals. These measurements are then put into a mathematical formula, resulting in an ASTA Pungency Unit. For those who prefer the use of the Scoville measurements though, you can “safely” convert the ASTA pungency units onto the Scoville Scale by multiplying the ASTA result by 16, for example, if you had 1 part capsaicin per million parts, this would equate to 1 unit on the ASTA scale and 16 on the Scoville Scale.

Reasons for using the Scoville Scale then; bigger numbers = better! Why say you have a pepper that is 100,000 ASTA units when you could say it is 1.6 million Scoville units? It sounds more impressive when you add more 0’s onto the end of the number. It is also easier to produce results than HPLC and at the end of the day, gives you a good estimate on what the peppers heat will be.

If you enjoyed this post, make sure you keep an eye out for an upcoming post where we show you how you can run your own similar tests to work out how hot your peppers are!

Keep it spicy!

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