Capsaicin is found mainly in the interior tissue to which the seeds adhere.
It has at least five separate chemical components. Three give the sensation in the throat and at the back of the palate while the other two give a slower, longer-lasting sensation and less fierce sensation on the tongue and mid-palate.
Ironically, capsaicin in odourless and flavourless. It is barely soluble in water; therefore, easing the pain with that substance does little good. They do dissolve in milkfat or alcohol, which is why many hot dishes are served with a milk dish.
Peppers vary in not only pungency but also their bite. A pepper that is extraordinarily hot on the Scoville scale
can, in fact, be more agreeable to the tongue than another pepper whose heat is very low.
For instance, the habanero offers a sharp and violent bite; but it quickly disappears, leaving a soothing and aromatic sensation behind. The eater, basking in this euphoria, hardly remembers that he was savagely attacked just moments ago.
Variations occur in the mouth as some peppers burn toward the back of the mouth, some burn the lips more than the tongue, and some make their presence known in the middle of the tongue.
These quirks result from the elemental parts that comprise capsaicin, called capsaicinoids, that vary in chemical structure. This is being looked at very closely by pepper researchers and merchants alike.
The chemical responsible for the pepper’s pungency was first isolated by an Englishman in India in 1877, and later identified as 8-methyl-N-vanillyl-6-nonenamide. Since then, researchers have isolated a dozen or so individual compounds that make up capsaicin.
Each capsaicinoid differs slightly in chemical structure. Essentially, each structure is a hexagon, attached to an open zigzag chain of carbon atoms.
The hotness diminishes as the chain lengthens or shortens, suggesting that there is a midpoint at which hotness peaks. This may explain why some peppers have an immediate “bite”, while others only cause moderate discomfort.
The perception of heat is felt when the chain gets to be three or four carbons long, and disappears when the chain is longer than eleven. The hottest range seems to be eight or nine carbons in length.
The increasing understanding of how capsaicin acts on Substance P (P stands for Pain) has created a surge of interest among neuroscientists. Extensive experiments with animals show that capsaicin relieves pain first by selectively attracting and then destroying the messengers responsible for taking the pain messenges to the brain.
When capsaicin is applied to the body, it first attracts Substance P (SP) from the nerve endings at the contact point. SP then starts to signal a burning sensation to the brain, but capsaicin soon begins to destroy the attracted messengers. As more SP is sent, it, too, is destroyed.
Capsaicin bleeds the neurons of SP until they no longer manufacture it. As a result, there are no more pain messengers left where capsaicin has been applied, and the sensory nerve endings become insensitive to chemically induced pain.
What is extraordinary, according to these scientists, is that capsaicin destroys only the pain messengers and leaves intact in the neurons, others charged with relaying tactile sensations – physical pain, heat, cold, taste, etc.
Such is not the case when anesthetics are administered or when a nerve is severed to relieve chronic pain. Pharmaceutical companies are finally beginning to exploit this unique attribute of capsaicin, which has long been the active ingredient in muscle relaxants and topical creams.
The Scoville Scale refers to the number of times that extracts of chillies dissolved in alcohol can be diluted with sugar water before the capsaicin can no longer be tasted. It was developed by a pharmacist named Wilbur Scoville, and became known as the Scoville Organoleptic Test.
Scoville had been studying the pharmacological uses for the pepper, but became frustrated with the many variables. Complaining in the 1912 issue of the Journal of the American Pharmaceutical Association, Scoville felt it would be better, when ordering peppers, if their pungency could first be assertained on a measureable scale.
He knew that the tongue was the most sensitive area able to detect capsaicin, the compound responsible for the pungency in peppers.
Because capsaicin is soluble in alcohol, Scoville was able to soak them and extract the pungent chemical from the pods. From this extract, he took a precise measurement and added definite amounts of sweetened water until the mixture’s pungency was barely preceived on the tongue.
In the case of Japan chiles, it took sweetened water in volumes between 20,000 and 30,000 times the pepper extract before the pungency was barely discernible.
Thus, he rated those chilis as 20,000 to 30,000 Scoville Heat Units. This system was used until the invention of a machine that could detect the hotness of a chili.
The machine, called HPLC (high pressure liquid chromatograph), looks like a $30,000 stereo. However, it never tires of testing pepper pungency.
Humans, on the other hand, can test only a limited number of peppers a day. Not only that, but no two tongues perceive the same pungency; whereas the machine is more reliable.
To test by machine, capsaicin is put into a tube under high pressure and then is exposed to a beam of light. Since capsaicin fluoresces, that is, lights up, the stronger the hotness or pungency of the pepper, the brighter the light. This measurement is then transposed onto a graph, which looks much like a seismograph, complete with peaks and valleys.
Capsaicin is actually composed of several individual compounds, with each representing a unique type of pungency. The peaks of all the curves are added to designate the pepper’s pungency.
While the tongue was able to test only about six samples per day, the machine is able to do thirty samples in eight hours.
Although the American Spice Trade Association is a strong proponent of the machine, Scoville’s name is so well established that the association has had about as much success in making people adopt their scale as the US government has had in adopting the metric system.
According to the Scoville scale, the following peppers range from the mildest to the hottest:
Anaheim – between 250 and 1400 units
Poblano – about 3000
Hungarian Yellow – 4000
Jalapeño (which can be red or green) – between 3500 and 4500
Serrano – between 7,000 and 25,000
Arbol (Chile de arbol) – between 15,000 and 30,000
Tabasco – between 30,000 and 50,000
Japanese santaka – between 50,000 and 60,000
Mexican tabiche – about 100,000
Cayenne – between 100,000 and 105,000
Indian birdeye – between 100,000 and 125,000
Japanese kumataka – between 125,000 and 150,000
Habanero – averages 300,000 (or lethal!)