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The Scoville Heat Unit explained

TheChilliGuyBlog mixed superhot chillies

The Scoville Heat Unit in detail

So how hot is a  Super Hot Chilli then and how is the heat measured I hear you ask?
Enter the wonderful world of the Scoville Heat Unit also known as SHU.  When you see a Dorset Naga being measured at over 1,000,000 SHU you now know its Scoville Heat Unit rating but how is that actually measured and how accurate is it?

Naga Chillies - Scoville Heat Unit
Super Hot Chillies – Image ©

A little history

In 1912 a pharmacist called Wilbur Scoville created a system whereby the amount of capsaicin level was measured and although there can be significant variation between chilli pods the scale serves to be indicative of the heat in a particular variety. He was looking to create a heat-producing ointment. What Scoville’s idea was, was to dilute an alcohol based extract made with the subject of the heat test until it no longer tasted  hot.

Wilbur Scoville - Scoville Heat Unit
Wilbur Scoville –
By College Yearbook – Henrietta Benedictis Health Sciences Library, Massachusetts College of Pharmacy and Health Sciences, Public Domain,

The amount of dilution directly corresponds to the Scoville Scale so in the case of Tabasco Sauce with a Scoville Heat Unit of 2500 to 5000, one would need 2500 to 5000 cups of water  to 1 cup of tabasco sauce  before the heat was no longer rated by the testers.

Typical Scoville Heat Unit levels for various chillies and peppers are:

  • 0 to 120 SHU – Mild Bells
  • 100 to 500 – Sweet Cherry
  • 2500 – 5000 – Jalapeno, Tabasco sauce
  • 30,000 – 50,000 Tabasco
  • 100,000 – 450,000 – Scotch Bonnet, Habanero
  • 450,000 – 500,000 – Fire Chillies
  • 900,000 – 1,000,000 Bengle Naga
  • 2,000,000 Scorpion Chilli

Tasters fatigue was soon found to be a problem where taste receptors were overused and couldn’t taste the heat any more.

Now we use a system called High Performance Liquid Chromatography. This means we can now calculate how many parts per million of alkaloids (heat causing chemicals) are present in a given chilli pod. It has also been discovered that if the alkaloid content is multiplied by 16 then the original Scoville Heat Unit (or very close to it) is arrived at. Chillies are dried , ground then the chemicals that are responsible for the pungency are extracted and tested. Altogether a much more accurate way to measure the heat

Dr Paul Bosland is professor of horticulture at New Mexico State University. He and his colleagues have developed a heat profile system where the chilli pepper heat profile  is broken into 5 different characteristics.

  • How hot is it?
  • How quickly does the heat hit?
  • How long does the heat last?
  • Where do you sense the heat?
  • Is the heat flat or sharp?

Borland further states that eating chillies can be compared to experiencing wine. At first you only taste the alcohol – then you can taste red or white – soon you can taste the differences between varieties.

Is there any truth about chilli addiction?

Well the science is quite clear. when you eat chillies a chemical in the chilli called Capsaicin acts as an irritant on the trigeminal cells. These cells are the pain receptor cells in the mouth, nose and throat. When your nerves feel the pain they transmit this ‘pain’ to the brain. The brain responds by releasing endorphins which act as a pain killer and also create a feeling of euphoria – a natural ‘high’ – Heart rate increases, metabolism increases, salivation increases and body sweating increases. Those that love hot and spicy food soon crave the euphoria that comes with the chilli hit.

Please feel free to get in touch with us here at The Chilli Guy. We’d love to hear about you chilli eating and growing successes and indeed failures. It’s all about sharing and learning good practices.

Until next time – happy chilli growing and eating. logo
The Chilli Guy


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