The chilli pepper (also chili or chile) is the fruit of the plant Capsicum, a relative of the tomato in the nightshade family (Solanaceae) Cultivated since prehistoric times in Peru and Mexico, it was discovered in the Caribbean by Columbus and named a "pepper" because of its similarity with the Old World peppers of the Piper genus. Diego Alvarez Chanca, a physician on Columbus' second voyage to the West Indies in 1493, brought the first chilli peppers to Spain, and first wrote about their medicinal effects in 1494.

The most common species of chilli peppers are Capsicum annuum, which includes many common varieties such as bell peppers, paprika, and jalapeños; Capsicum frutescens, which includes the cayenne and tabasco peppers; Capsicum chinense, which includes the hottest peppers such as habaneros and Scotch bonnets; Capsicum pubescens, which includes the South American rocoto peppers; and Capsicum baccatum, which includes the chiltepin.

In the 'old days' before chemists, ancient civilizations used chilli as a remedy for a sore throat; they would cobble together a paste with yellow chilli and honey. If it persisted, they drank an infusion of salt and chilli - Yum!! There are some tribesmen that still use it to today.

 A man made version of Capsaicin (the 'hot' substance in chilli), Guafenesein, is used in many modern cough syrups. 

What Makes Chilli Hot?

The substances that give chillies their heat are the alkaloid capsaicin (8-methyl-N-vanillyl-6-nonenamide) and four related chemicals, collectively called capsaicinoids.

Capsaicinoids are the name given to the class of compounds found present in members of the capsicum family of plants.  The most common of these compounds is Capsaicin, which is found in the white ‘ribs’ inside hot chillies. Capsaicin probably evolved in plants as a protective mechanism, to discourage certain pests. Different species of chilli contain different amounts of capsaicin, conferring different degrees of "hotness".

Each capsaicinoid has a different effect on the mouth, and variation in the proportions of these chemical is responsible for the differing sensations produced by different varieties. Capsaicin causes pain and inflammation if consumed to excess, and can even burn the skin on contact in high concentrations (habanero peppers, for example, are routinely picked with gloves). It is also the primary ingredient in pepper spray, which is used as a defensive weapon. The "heat" of chilli peppers is measured in Scoville units. Bell peppers rank at zero Scoville units, jalapeños at 3,000–6,000 Scoville units, and habaneros at 300,000 Scoville units.

The record for the highest number of Scoville units in a pepper is assigned by the Guinness Book of Records to the Red Savina Habanero, measuring 577,000 units! However, a recent report was made of a pepper from India called the Naga Jolokia measuring at 855,000 Scoville units. Both the Red Savina and the Naga Jolokia claims are disputed as to their validity, and lack independent verification.

In 1912 Wilbur Scoville proposed a scale of measurement based on the apparent hotness of extracts placed on the tongue after dilution. Thus, bell chillies have a rating of less than 1 Scoville unit, jalapeno chillis 10³ units, Habanero chillis 10⁵ units, and pure capsaicin 10⁷ units.

It was first a subjective taste test, but since, it has been refined by the use of HPLC, the unit is named in after of its inventor.

Of course, being a natural product, the heat can vary from chilli to chilli, so this scale is just a guide.

Chemistry and Scoville Units

It was in 1912 whilst working for the Parke Davis pharmaceutical companies that one of their chemists, Wilbur Scoville, The Scoville Organoleptic Test, developed to measure the heat level of a chilli pepper, with a dilution-taste procedure. In the original test, Scoville blended pure ground chillies 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 chilli based on how much it needed to be diluted before you could taste no heat.  The pungency of chilli 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 chilli "heat" per 1,000,000 drops of water rates as only 1.5 Scoville Units.

 The validity and accuracy of the above 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.

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

The following is a list of chilli that we have grown this year and their relative pungency levels and their Scoville Heat Units.

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Last modified: 11/11/07