Chemistry and Scoville Units

It was in 1912 whilst working for the Parke Davis pharmaceutical company that one of their chemists, Wilbur Scoville, developed a method to measure the heat level of a chile pepper. This test is named after him, it's called the Scoville Organoleptic Test, and it's a dilution-taste procedure. In the original test, Scoville blended pure ground chiles with a sugar-water solution and a panel of testers then sipped the concoctions, in increasingly diluted concentrations, until they reached the point at which the liquid no longer burned the mouth. A number was then assigned to each chile based on how much it needed to be diluted before you could taste no heat.

The pungency of chile peppers is measured in multiples of 100 units, from the bell pepper at zero Scoville units to the incendiary Habanero at 300,000 Scoville units! One part of chile "heat" per 1,000,000 drops of water rates as only 1.5 Scoville Units. The substance that makes a chile so hot (and therefore so enjoyable to Chile-Heads !), is Capsaicin. Pure Capsaicin rates over 15,000,000 Scoville Units !


The "Red Savina" Habanero has been tested
at over 577,000 Scoville units!

This is so much hotter than the normal Habanero chile pepper, that the "Guinness Book of Records" have accepted it as "the hottest chile pepper" in the world. Even now, breeders are attempting to beat this. The new Francisca Habanero is said to be hotter still!

Stop Press

The new title holder, according to experts at the Defence Research Laboratory in the army garrison town of Tezpur in the north-eastern state of Assam, is the local Naga Jolokia (capsicum frutescens).

It was nearly 50 per cent more pungent than the Red Savina Habanero from Mexico.

"Laboratory tests have confirmed that Naga Jolokia, a specialty from the north-east, is now the world's hottest chilli," the laboratory's deputy director S.C. Das said by telephone from Tezpur.

The naga jolokia is grown mostly in the hilly terrain of north-east India and is a staple in every meal among local tribals.

Read further about the Naga Jolokia at:

The Daily Star Internet Edition @

SAfm Headlines @

India Abroad News Service @


The validity and accuracy of the Scoville Organoleptic test have been widely criticised. The American Spice Trade Association and the International Organisation for Standardisation have adopted a modified version. The American Society for Testing and Materials is considering other organoleptic tests (the Gillett method) and a number of other chemical tests to assay for capsaicinoids involved in pungency. Even so, the values obtained by these various tests are often related back to Scoville Units. Nowadays the High-Performance Liquid Chromatography (HPLC) test is used. In this procedure, chile pods are dried, then ground. Next, the chemicals responsible for the pungency are extracted, and the extract is injected into the HPLC for analysis. This method is more costly than the previous, but it allows an objective heat analysis. Not only does this method measure the total heat present, but it also allows the amounts of the individual capsaicinoids to be determined. In addition, many samples may be analyzed within a short period.


As a result of all these tests, various varieties of chile peppers can be ranked according to their heat or "pungency" level:

     Ball   0-100 Scoville Units includes most Bell/Sweet pepper varieties.
     Ball   500-1000 Scoville Units includes New Mexican peppers.
     Ball   1,000-1,500 Scoville Units includes Espanola peppers.
     Ball   1,000-2,000 Scoville Units includes Ancho & Pasilla peppers.
     Ball   1,000-2,500 Scoville Units includes Cascabel & Cherry peppers.
     Ball   2,500-5,000 Scoville Units includes Jalapeno & Mirasol peppers.
     Ball   5,000-15,000 Scoville Units includes Serrano peppers.
     Ball   15,000-30,000 Scoville Units includes de Arbol peppers.
     Ball   30,000-50,000 Scoville Units includes Cayenne & Tabasco peppers.
     Ball   50,000-100,000 Scoville Units includes Chiltepin peppers
     Ball   100,000-350,000 Scoville Units includes Scotch Bonnet & Thai peppers.
     Ball   200,000 to 300,000 Scoville Units includes Habanero peppers.
     Ball   Around 16,000,000 Scoville Units is Pure Capsaicin.

Capsaicin, also known as N-Vanillyl-8-methyl-6-(E)-noneamide, is the most pungent of the group of compounds called Capsaicinoids that can be isolated from chile peppers. It is sparingly soluble in water, but very soluble in fats, oils and alcohol. The minor Capsaicinoids include Nordihydrocapsaicin [Dihydrocapsaicin with a (CH2)5 instead of (CH2)6], Homocapsaicin [Capsaicin with a (CH2)5 instead of (CH2)4, and Homodihydrocapsaicin [Dihydrocapsaicin with a (CH2)7 instead of (CH2)6]. 

Here, causing some of the "pain", is the chemical composition of the better known of the Capsaicinoids
(courtesy of John Henninge M.Sc.)






Capsaicin and Dihydrocapsaicin together make up 80-90% of the Capsaicinoids found in peppers. In the Capsicum annum species, the total Capsaicinoid content ranges from 0.1 to 1.0%, and the Capsaicin to Dihydrocapsaicin ratio is about 1:1. In Capsicum frutescens the total content ranges from 0.4-1.0% with the ratio around 2:1.

Given all these various molecules, tests have shown that the Capsaicinoids can be ranked according to their heat or "pungency" level:     

Ball   At 8,600,000 Scoville Units is Homocapsaicin.

     Ball   At 8,600,000 Scoville Units is Homodihydrocapsaicin.

     Ball   At 9,100,000 Scoville Units is Nordihydrocapsaicin.

     Ball   At 16,000,000 Scoville Units is Dihydrocapsaicin.

     Ball   At 16,000,000 Scoville Units is Pure Capsaicin.

In order to douse the heat when eating chile peppers, try drinking milk or eating ice cream or yoghourt. These dairy products are especially effective at breaking down the Capsaicin oils, which are not soluble in water.

For more detailed chemistry of Capsaicin and other vanilloids, the Frostburg State University has a very good web page with some useful links to other sites.

The Brooklyn Botanic Garden has an interesting article by Paul Bosland on

'What makes Chile Peppers hot?'

"The least irritating capsaicinoid is nordihydrocapsaicin, according to researchers at the University of Georgia. They found that the burning is located in the front of the mouth and palate, causing a "mellow warming effect." The pungency sensation develops immediately after swallowing and recedes rapidly. In comparison, capsaicin and dihydrocapsaicin were found to be more irritating, and were described as having a "typical" pungency sensation. Both compounds produce pungency in the middle of the mouth, the middle of the palate, the throat, and the back of the tongue. In contrast, homodihydrocapsaicin is very irritating, harsh, and very sharp. The pungency does not develop immediately but it affects the throat, back of the tongue, and the palate for a prolonged period."

Other compounds

A recent paper in Journal. Sci. Food Agric., 1995, 67, 189-196 by S.M. van Ruth, J.P. Roozen and J.L. Cozijnsen, and available at The Department of Chemistry, University of the West Indies, describes flavour components in Bell peppers. Out of 47 compounds identified, 12 could be detected by assessors at a sniffing port on a Gas Chromatograph: 

other compounds found in reasonable quantities were: 

The compound described as the character imparting compound in Bell peppers is 2-isobutyl-3-methoxypyrazine. This very powerful odourant has a threshold in water of 1 part in 10^12.

Beer and water will only spread the flames !!

The following information is a guide to the process for the crude purification of Capsaicin that I found on the net.

Follow it at your own risk !


15 Habanero peppers

1 quart 200 proof Ethanol


In a blender, puree the Habanero's in as much Ethanol as possible. Let the mixture sit overnight at room temperature. Pour the resultant sludge through paper towels and place the liquid in a glass container. Begin to heat the liquid very slowly using either an electric heating device (naked flames would be dangerous), or use a vapour trap to remove the alcohol fumes safely. Continue until 90% of the liquid has evaporated. Remove from the heat and let cool. Look for a brick-red oil floating on the surface of the ethanol. If none is present, continue to evaporate the ethanol away periodically cooling the mixture to look for the red oil on the surface. Once the red oil appears, pour the red oil and the remaining ethanol into a long thin glass cylinder, use an eye dropper to suck off the oil and place it in a clean container. The red oil is fairly pure Capsaicin, probably 40% Capsaicin / 60% Capsaicinoids.

Please bear in mind that Capsaicin is an extreme irritant and is hazardous to health as both a chemical burn agent and as a poison when in its purer concentrated forms. Only a fool or a chemist would want to undertake the above procedure

See Sigma-Aldrich publications for further information

Suggested reading and references

Many thanks to the Sunday Times for the review in the following article:

June 3 2001 DOORS 

Feeling hot?     Robbie Hudson is sweltering too 


Another way of experiencing heat is to visit, which sells hot sauces that are doubtless bought by the kind of sane people who call themselves mad. How could such a person resist DOA Cyanide Hot Sauce or the Blair collection (After Death, Death Rain, Original Death and Sudden Death). The most interesting section compares pepper strengths, ranging from jalapeņo at a pathetic 10,000 Scoville units to the undeniably perky habanero at 300,000 Scovilles. "Scovilles" are the number of units of water needed to render a unit of pepper untingly (a scientific term) to the human tongue, based on the lunatic experiments of Wilbur Scoville. 
Testing is now carried out using liquid chromatography, as the helpful explains. It also informs you that the hottest pepper is the red savina (577,000), and reveals how to refine pure capsaicin (a terrifying 15m Scovilles). It adds that only a fool would do this.
Drinking aftersun lotion will not soothe any resultant burning.