One of the most remarkable things about crops is they are just so amazingly variable compared to wild plants. Think for a moment about how many different varieties of apples there are compared to their uniform small green ancestors, or flick through any seed catalogue and almost every single type of fruit or vegetable is available as several different varieties, each with its own exotic sounding name. Humans just love variety and over the years we have excelled in producing a vast array of variation in the plants we cultivate and eat. The chilli is a fine example of this to the extent it even has a unique scientific scale for measuring its own particular form of fiery variation.
Chillies are among the oldest cultivated plants from the New World tropics. A team from the Smithsonian have recently claimed to have found evidence of chilli consumption in Ecuador more than 6000 years ago. Today chillies are cherished around the globe and are used in ‘traditional’ recipes in Africa, Asia, and Europe and from home territory in the Americas and the Caribbean. Chillies are available in a dazzling array of different forms, from sizzling hot habañero and Tabasco peppers to the mildest of sweet pimentos; they vary in size and shape from small and thin bird-peppers to large and round bell-peppers, the fruit are reds, greens, yellows golden to almost white, purple to virtually black. Actually this rainbow of variation is rather cheating, because it does not represent a single species. Chillies are one of a small group of crops in which several species are all grouped together as one. In the case of chillies, five related species have been domesticated on different occasions. The most widely grown is Capsicum annuum which originated in Mexico and the Southern United States. Moving south, is the inappropriately named C. chinense and the very closely related C. frutescens from the Caribbean and Northern South America, these give us the hot Tabasco and Caribbean Scotch Bonnets. In the heart of South America and the high Andes are another two species, but these are little cultivated outside the region.
Biologically the entire purpose of a fruit is to attract the attention of a hungry animal and then to be consumed and thus act as a dispersal mechanism for the seeds within. This is why fruit ripen to bright attractive colours, and become sweet and delicious just as the seeds are ready to leave home. But this raises the obvious question, if that is true, why are some fruit poisonous or burning hot like the chilli? The answer to this riddle is it rather depends on who you are trying to attract. If seeds are consumed by the wrong species of animal, instead of being conveniently dispersed to a suitable location with a little pile of fertilizer, they end up being digested along with the surrounding fleshy fruit. This is where the chilli is a real master. Capsaicin the chemical which gives chilies their fiery hotness specifically targets the nerve endings of mammals causing exactly the same reaction in the brain as being physically burnt, but capsaicin is completely benign to birds. It is no surprise therefore to learn that birds are effective dispersal agents of chilies. In contrast chilli seeds are usually destroyed in the guts of the few mammals brave enough to risk being burnt.
Humans as so often in life are just perverse, and many of us are actively attracted to the burning hotness that is caused by eating chilies. To the extent that they search out ever hotter varieties as their nerves become desensitized to the capsaicin and plant breeders compete to produce increasingly hotter varieties to supply these chilli junkies. In 1912 the chemist Wilbur Scoville invented a scale for describing the hotness of chillies. This involves dissolving a sample of chilli in sugar solution and diluting it until the point that the heat is no longer detectable by a panel of five volunteer tasters. The Scoville scale ranges from the sweetest bell-peppers at zero on the scale to 16,000,000 for pure capsaicin, the mighty scorching habañeros are around 350,000 to 580,000 which are mild compared to the ludicrously nuclear naga chili at 923,000. These are sold with extreme health warnings and are best handled only with gloves.
The Scoville scale actually demands a little more explanation, because capsaicin is insoluble in water but is soluble in alcohol. Therefore the sample of chilli to be tested must first be dissolved in a known volume of alcohol before being mixed with sugar solution. This is said to be the reasons that you are not recommended to drink water to extinguish the flames of chilli incendiary device, but a beer might be more effective. But then-again without the beer you may never have turned arsonist in the first place and in reality, the alcohol content of beer is so low that it is not sufficient to effectively dissolve enough capsaicin to quench the fire. Even so a hot chili and a cold beer remains a classic combination.