Professor Wilber L. Scoville

In 1912 a chemists by the name of Wilbur Scoville, working for the Parke-Davis pharmaceutical company, developed a method to measure the heat level of chile peppers. The test is named after him, the "Scoville Organoleptic Test". It is a subjective dilution-taste procedure. In the original test, Wilbur blended pure ground Chiles with sugar-water and a panel of "testers" then sipped the solution, in increasingly diluted concentrations, until they reached the point that the liquid no longer burned their mouths. A number was then assigned to each chile pepper based on how much it needed to be diluted before they could no longer taste (feel) the heat.

"1,000,000 drops of water is rated at only 1.5 Scoville Units" The pungency (or heat factor) of chile peppers is measured in multiples of 100 units. The sweet bell peppers at zero Scoville units to the mighty Naga Jolokia (Ghost Pepper) at over 1,000,000 Scoville units! One part of chile "heat" per 1,000,000 drops of water is rated at only 1.5 Scoville Units. The substance that makes a chile so hot is called Capsaicin (cap-say-ah-sin). Pure Capsaicin rates between 15,000,000 and 16,000,000 Scoville Units! Today more scientific and accurate methods like Electrochemistry and High Performance Liquid Chromatography (HPLC) are used to determine capsaicin levels. In honor of Dr. Wilbur the unit of measure is still named Scoville. Below is a list of Chile peppers and their Scoville Heat Units. Due to variations in growing conditions, soil and weather, peppers tend to vary between the lower and upper levels listed, but can go beyond them.

 

A Little Chile Chemistry For
The Visiting Rocket Scientist

Chiles are members of the Capsicum family. Heat range is diverse, ranging from very mild to extremely wild. The particular class of substances that determine their disposition is known, by those who study such things, as Capsaicinoids. The two most common component of this class are Capsaicin and Di-Hydrocapsaicin they looks something like this.

                    H3CO
                      \____       O            CH3
                      /    \      |            |
                  HO-<      >-C-N-C-(CH2)4-C=C-C-CH3
                      \____/  | |          | | |
                             H2 H          H H H

   

                    H3CO
                      \____       O        CH3
                      /    \      |        |
                  HO-<      >-C-N-C-(CH2)6-C-CH3
                      \____/  | |
                             H2 H
            
   

Capsaicin and Di-hydrocapsaicin together make up 80-90% of the Capsaicinoids found in Chile 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.

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].

The different capsaicin-like compounds found in Chiles have slight structural variations in the hydrocarbon tail, changing their ability to bind to the nerve receptors and their ability to penetrate layers of receptors on the tongue, mouth, and throat. This may explain why some Chiles burn in the mouth, while others burn deep in the throat.

Capsaicinoids are not soluble in water, but very soluble in fats, oils and alcohol. This is why drinking water after accepting a dare to eat an extra hot Habanero Chile won't stop the burning. Downing a cold beer is the traditional remedy, but the small percentage of alcohol will not wash away much capsaicin. To get some relief from a chile burn (can't think of a good reason not to "Enjoy the heat"), drink milk or eat ice-cream. Milk contains casein, a lipophilic (fat-loving) substance that surrounds and washes away the fatty capsaicin molecules in much the same way that soap washes away grease.

The perception that peppers are "hot" is not an accident. The capsaicin key opens a door in the cell membrane that allows calcium ions to flood into the cell. That ultimately triggers a pain signal that is transmitted to the next cell. When the cells are exposed to heat, the same events occur. Chile burns and heat burns are similar at the molecular, cellular, and sensory levels.

Paradoxically, capsaicin's ability to cause pain makes it useful in alleviating pain. Exposure to capsaicin lowers sensitivity to pain, and it is applied as a counter irritant in the treatment of arthritis and other chronically painful conditions.

The capsaicinoids are unique compared to other spicy substances, such as piperine (black pepper) and gingerol (ginger) in that capsaicin causes a long-lasting selective desensitization to the pain and discomfort, as a result of repeated doses. The result is an increasing ability to tolerate ever hotter foods and permits one to assume the title of "Chile-Head" or "CH" for short.

People that eat lots of spicy capsaicin-rich foods build up a tolerance to it. The incentive: Once a person has become somewhat desensitized to the extreme heat of the "hotter" Chiles, he or she can starts on a new culinary journey. Not being over powered by the heat factor, the palate now has the ability to explore the many diverse flavors offered by the myriad of different Chiles that are currently available from around the world. Also for some Chile-Heads a good jolt of capsaicin excites the nervous system into producing endorphins, which promote a pleasant sense of well-being that can last several hours. The endorphin lift or "high", makes spicy foods mildly addictive and for some, an obsession.

I offer the below information and pictures for folks that are really into the science of Chiles.

Date: Mon, 26 Feb 2001
Uncle Steve,

Here are the images as promised. I included structures of some of the minor capsaicinoids as well.

There are two versions (a and b) of each structure, corresponding to different conventions of drawing. They're equally correct and unequivocal, and you're free to choose whichever version you prefer. The 'a' convention is most commonly used by chemists, but the 'b' convention might be a bit easier to understand for non-chemists.
Best regards,
John Henninge

 

Melting point: 65 ° C
Boiling point: 210-220 ° C at 0.01 torr pressure
Sorce: The Merck Index. 12th Edition. Merck & Co., Inc. Whitehouse Station, NJ. 1996.

Still need more HOT Chile Pepper information?