This once simple test is now far more advanced and way more accurate than it was when first devised but the name lives on!
The Scoville scale is a measure of the 'hotness' of a chilli pepper or any products containing or made with chilli peppers, i.e. hot sauce, salsa etc.. The scale is actually a measure of the concentration of the chemical compound capsaicin (pronounced Cap-Say-Uh-Sin) which is the active component that produces the burning sensation we are all familiar with.
The scale or test is named after Wilbur L. Scoville (1865-1942), who developed the Scoville Organoleptic Test in 1912 while working at the Parke Davis pharmaceutical company. The test he devised is as follows: a solution of the pepper extract is diluted in sugar water until the 'heat' is no longer detectable to the human tongue. A panel of tasters was used to evaluate results and the degree of dilution gives its measure on the Scoville scale. A Bell pepper for example has a Scoville rating of zero (no heat detectable even undiluted) as it contains no capsaicin. However, the hottest chillies, such as Nagas have a rating of 1,000,000 or more, which means that their extract would have to be diluted with at least 1,000,000 equal parts of sugar water before the capsaicin present is undetectable. The greatest weakness of the Scoville Organoleptic Test is its imprecision, because it relies on human subjectivity.
The name capsaicin comes from the scientific classification of the pepper plant, a type of fruit, that belongs to the genus Capsicum.
Capsaicin (8-methyl N-vanillyl 6-nonenamide) occurs naturally in chilli peppers together with a number of very similar compounds referred to generically as capsaicinoids. It is the amount of these capsaicinoids which causes the differences in “heat” and taste in different pepper species. For example the typical delayed reaction to the habanero pepper (C. chinense) as compared to other species.
Nowadays, capsaicin concentrations are measured using more scientific methods, typically High Pressure Liquid Chromatography (HPLC). This direct measurement of capsaicin gives much more accurate results than sensory methods, which are deemed highly subjective.
The Scoville rating or 'hotness' of fresh chillies is obviously dependent
upon the variety of pepper but even within one particular variety the hotness can vary greatly. No chilli plant is the same, indeed no chilli fruit on the same plant is the same. Factors influencing the heat of a fresh pepper include growing temperature, hours of sunlight, moisture, soil chemistry, and the type and amount of fertiliser used.
It is believed that the more “stress” a plant undergoes, the hotter it’s fruit will be. Examples of stress would be too much or too little light, water, even wind.
For many years the Guinness Book of World Records listed the world’s hottest chilli pepper as the Red Savina Habanero. Generally these peppers range from 350,000–570,000 Scoville Units as compared with a score of 2,500–5,000 for the Jalapeno pepper. The record breaking pepper was produced by GNS Spices Inc in 1994 in Walnut, US and measured at 577,000 Scoville units.
In recent years however, several super-hot peppers have challenged for the record. Experts at the Defence Research Laboratory in the army garrison town of Tezpur in the North-Eastern state of Assam, claimed a locally grown Naga Jolokia in testing was nearly 50 per cent more pungent than the red savina habanero at a blistering 855,000 Scoville units. However, this remained unsubstantiated. Seeds of the same Naga- Bih Jolokia pepper (sometimes also called the Bhut Jolokia) cultivated at New Mexico State University were tested in Fenruary 2007 when a specimen registered a staggering 1,001,304 Scoville heat units and was officially acclaimed by the Guinness World Record as the new worlds hottest pepper. The Naga Jolokia is nearly twice as hot as the previous record holder, the Red Savina.
Just recently various strains of Naga have been grown in the UK to heat levels of up to 1,382,118 Scoville Heat Units (SHU) at the time of writing this and the race to have the hottest continues……