What makes Chiles Hot?

Most chileheads know that a chemical called Capsaicin is what gives Chiles their heat. But what is it and where does it come from? Why can some people eat a hot habanero with ease, yet others break out in a sweat at the mere thought? Is the Morouga Scorpion really the world's hottest Chile? This chileman's guide aims to answer some of these questions as well as providing some advice on how to avoid 'Hunan hand', 'Jalapeno eye' and tackle the burn!

But first let me start with some of my favourite quotes:

"Pure capsaicin is so powerful that chemists who handle the crystalline powder must work in a filtered "tox room" in full body protection. The suit has a closed hood to prevent inhaling the powder. It's not toxic, but you wish you were dead if you inhale it."
Lloyd Matheson of the University of Iowa

Scary eh? However, before explaining how this nasty little substance is produced by your beloved Chile plants you first need to have a little chemistry lesson.

Capsaicinoids - A brief Chemistry Lesson

It is a series of complex chemical compounds called capsaicinoids that are responsible for giving Chiles their bite. Capsaicin is the most famous (and the most pungent) although scientists have identified and isolated other natural members of this fiery family (Dihydrocapsaicin, Homodihydrocapsaicin, Nordihydrocapasaicin) and one synthetic cousin (Vanillyamide). The latter is used as a reference point for determining the relative pungency of the others.



Capsaicin & Dihydrocapsaicin are typically responsible for about 80-90% of the capsaicinoid content of a pepper and hence are the source of most of the heat. The balance of the bite is made up by the presence of one or more minor capsaicinoids.

When Chiles are eaten, the capsaicinoids irritate the tigeminal cells (pain receptors located in the mouth, nose and stomach), which release a chemical known as substance P into blood which tells the brain you've eaten something hot. The brain responds by flushing the body with water to try and douse the flames, which is why after consuming a particularly hot Chile some people suddenly break into a sweat, their nose runs and their eyes start to stream.

The trigeminal cells are also connected to the production of endorphins, morphine like natural painkillers that produce a sense of well-being. It is the rush generated from the release of endorphins that is often cited as the reason why some chileheads become addicted to fiery foods. Repeated consumption of Chiles is also believed to confuse trigminal cells, which is also why some of your 'Chile monster' friends seem to have built up a tolerance to capsaicin and can, eat the hottest habanero without even flinching.

How and where is Capsaicin Produced?


Capsaicinoids are produced by the glands at the juncture of the placenta and the pod walls. It is spread unevenly throughout the inside of the pod although concentrated most in the central placental tissue. Contrary to popular believe seeds are not sources of heat. However because of their proximity to the placenta, they do occasionally absorb some capsaicin.

How is Heat measured?

Determining the precise pungency of Chile varieties has long been a goal of cooks, growers and researchers alike. Many heated arguments have taken place on Chile forums as to which is 'the world's hottest Chile'. The problem with the "official" record suggested by Guinness, is that they only take into account the highest test reading. The record is currently held by the Morouga Scorpion, which tested above 2 million SHU. That does not mean that every instance of this pepper will measure that heat level. In my damp, cold English greenhouse, I have sucessfully grown supposedly super hot peppers with very little heat.

Although both subjective and scientific measures have been developed, the arguments as to the hottest variety will never be solved, as pungency is pod specific. Aside for presence and concentration of capsaicinoids many other factors will determine the pungency of pods. These include local growing conditions, watering regimes, soil chemistry and even the type and amount of fertiliser used.

Some say that 'stressing your plants' by under watering/under feeding can produce hotter peppers. The obvious method to stress your plants is to get the wife to sit in your green house and talk to your plants on a regular basis. A suitably qualified mother in law is also an acceptable substitute!

As well as great variability amongst plants of the same variety, there will be also be much variability amongst pods on the same plant. Even when scientific laboratory tests have determine a precise heat level, the very subjective nature of individual taste will come into play as the different capsaicinoids have differing effects on peoples taste buds. This is why some people swear that Rocotos (with their own unique blend of capsaicinoids) are far hotter than Habaneros.

Scoville Heat Units (SHU)

In 1912, Wilbur L Scoville, a pharmacologist developed the Scoville Organoleptic test. This test is one of dilution and involved a brave panel of five people tasting increasingly diluted samples of solutions made from exact weights of Chile peppers dissolved in alcohol and diluted with sugar water. Several dilutions were tasted until the capsaicin (heat) could no longer be detected. One part capsaicin per 1,000,000 drops of water (about 1 gram per 7000 gallons of water) is rated at 1.5 Scoville Units.

However for many of the reasons above, it was soon evident that the test was highly subjective, and today it has replaced by High Pressure Liquid Chromatography (HPLC).

High Pressure Liquid Chromatography (HPLC)

High Pressure Liquid Chromatography (HPLC), sometimes called High Performance Liquid Chromatography is a laboratory based test which detects and measures the various capsaicinoids. A chile solution is placed into the chromatograph machine, and under high pressure, the machine separates the capsaicin from the total volume of liquid and thus calculates the concentration of the capsaicin in parts per million (ppm). For the diehard need-to-know chillihead, multiply the HPLC ppm figure by 16 will get you the approximate Scoville Heat rating. For example, if a total capsaicinoid content of 36000 mg/kg is determined, multiplying this value by 16 would mean 576,000SHU.

The 'Hot as Hell Hall of Fame'.

In 1994, a Red Savina Habanero from GNS Spices has tested what was, at the time, an astonishing 577,000 Scoville Units and was believed to be the hottest pepper ever tested. Since then a number of peppers have held the title, and you can read the full story here.

Although the heat level to a particular palette is highly subjective and can vary significantly from pod to pod, here is a very rough guide to the reported Scoville heat levels of some of the more common domesticated species and varieties:

Species*
Chinense above 1 million SHU
Frutescens up to 150,000 SHU
Annuum up to 100,000 SHU
Pubescens up to 50,000 SHU
Baccatum up to 30,000 SHU

Note that pure capsaicin is a mouth numbing 16,000,000 SHU!

This is a generalist guide as selective breeding programmes have created several very hot annuums and chinense varieties with little to no heat. Commercial growers are also well known for exaggerating SHU levels, as they all want to supply the hottest! The chart below is a rough guide to SHU, as more tests are done, the numbers keep changing.

Trinidad Scorpion2,000,000 SHU
Naga Morich1,041,000 SHU
Red Savina350,000 to 577,000 SHU
Habanero's & Scotch Bonnet's100,000 to 350,000 SHU
Chiletepins, Thai & Birds Eye50,000 to 150,000 SHU
Piquin, Cayenne, Tabasco & Rocoto30,000 to 50,000 SHU
De Arbol, Aji's & Shipkas15,000 to 30,000 SHU
Serrano5,000 to 15,000 SHU
Jalapeno, Mirasol & Hot Wax2,500 to 5,000 SHU
Anaheim, Rocotillo, Sandia & Cascabel1,500 to 2,500 SHU
Ancho, Pasilla, Mulato & Espanola1,000 to 1,500 SHU
Cherry, New Mexican500 to 1,000 SHU
Bell Peppers & Pimentos0 SHU


Hunan Hand and how to tackle the burn

Hunan hand' (also known as 'Chile Willy') is the name given to the skin irritation caused by capsaicin as a result of contact with Chile peppers. It is said to have obtained its name from an unfortunate young man who burst into a clinic in Chicago, waving his hands and moaning in pain. With some difficulty he described that he had been in the midst of preparing a Hunan Chinese lunch with hot peppers. 'Jalapeno eye' will also be known to Chile growing contact lens wearers.

Capsaicin, one of the most powerful chemicals know to man has no flavour, colour or odour and is unaffected by cooking, grinding or freezing. Although it is readily soluble in fats (like skin), pure alcohol and some oils it is not soluble in water which is why gulping down pints of water to fan the flames will simply swill the substance around your mouth and make it even worse! Downing pure alcohol would kill you and therefore is also a bad idea.

When handling hot Chile peppers, ALWAYS wear a pair of disposable gloves and preferably eye protection. Most Chile enthusiasts have heeded this warning at some time. Believe me you will only make this mistake once!

If you are unfortunate to get struck down by Hunan Hand, dowse the affected part with a mild bleach solution, vegetable oil or milk all of which will help easy the pain (in time). Do not using these treatments for Jalapeno eye! A cool wet towel and a lie down is probably the best remedy.