SCIENCE
How Hot Is It?
By Dr. Rizwana Rahim
Chicago, IL


How hot is it? If it is about spicy food, you can easily go through a routine Johnny Carson used to have about the weather: “It is SO hot that ….” But how can you say it scientifically? And, compare any two such items ?
We know it’s the pepper (chilli, chili or, in Spanish, chile), but what makes it hot, and why? Its ‘hotness’ or pungency is produced mostly in the white "ribs" that form the innermost layer of the cover/flesh that surrounds the seeds, and then, the seeds acquire it. Pungency in the rest of the fruit is not high, and is unevenly distributed. The color of the pod is the result of contribution from 20-plus carotenoids (capsanthin, found in the red and ripe pods, being the major carotenoid, up to 60% of the total).
The pungency is due to alkaloid compounds called capsaicinoids, more specifically a group of 7 homologous branded chain alkyl vanillylamides. Two of them, capsaicin and dihydro-capsaicin, are most abundant. They are present either in equal amounts or capsaicin is 2x more than the other. They make up about 80-90% of the total capsaicin oids. Capsaicin is a vanilloid, and this group includes vanillin, present in vanilla ! Capsaicin is similar to peperin, found in black pepper.
To scientifically determine the pungency of the pepper, an organoleptic test was developed nearly a hundred years ago (J. Amer. Pharmacists Assoc. 1: 453-454, 1912). It ‘digitalized’ the pungency in terms of ‘Scoville’ Heat Units (SHU), named after the developer, Wilbur Scoville, who was then working for Parke-Davis. Initially, it was based on the experience of a panel tasters, generally 5.& nbsp; It involved diluting the extract of the pepper with equal amounts of sugar water, over and over again sequentially, till the diluted extract has NO bite, pungency or ‘heat’, when tasted by the panel. The number of times pepper extract was diluted is its SHU. The hotter the pepper, the higher the score. For instance, a cayenne pepper extract has to be diluted with equal amounts of sugar water 25,000 to 50,000-fold before it loses its ‘hotness’. Because of this, it got 25,000-50,000 SHU. On the same scale, Jalapeno pepper got 2,500 to 5,000 SHU, that is, considerably less hot. The considerable SHU range fo r each pepper is mostly due to individual differences in reaction among the 5 tasters, and such highly subjective tests are fraught with problems, including the wide variation noticed.
A recent more sensitive and reliable chemical test was developed to measure what actually causes the ‘hotness’, i.e., capsaicinoids, by analyzing the extract with high-pressure liquid chromatography, HPLC, techniques (J. E. Woodbury, J. Assn. Offic. Anal. Chem. 63:556-558, 1980; M. D. Collins, et al. HortScience 30:137-139, 1995). The Scoville scale (a kind of Thermal Richter scale) ranges from the sweet or bell pepper (which has no capsaicin) at 0 SHU to pure capsaicin, which is the hottest at about 15,000,000 SHU. For getting SHU from the capsaicin amount measured by HPLC, multiply capsaicin (in ppm, or parts per million) by 15.
Some pepper varieties with increasing pungency are SHU (in parenthesis) : pimento and pepperoncini (100-500); Coronado (700-1,000); pablano (1,000-2,000); jalapeno (2,500-8,000); chipotle and hot-wax (5,000-10,000); serrano (5,000-23,000); tabasco & cayenne (30,000-50,000); chiltepin (50,000-100,000); Carolina cayenne (100,000-125,000); Scotch bonnet and habanero chile (100,000-350,000). The Guiness record holder has been Red Savina habanero (350,000-580,000). Then at 855,000 SHU (unverified) came Tezpur, Naga- or Bih- Jolokia chili (C. frutescens; 2 in long, half-inch wide when mature; orange color, similar to habanero). Jolokia was discovered in Tezpur, Assam, by Indian Defense Dept. scientists from Gwalior and Guwahati; if its SHU is confirmed, it’d be the hottest pepper in the world. Pungency can vary depending on the climatic and soil conditions and the maturity of the fruit. By genetic engineering and breeding, scientists have been able to modify/manipulate pungency as well as other properties.
Pepper/chilli/chili/chile is a fruit belonging (botanically) to Solanaceae family that includes tomato, eggplant, potato and tobacco. Pepper belongs to the genus Capsicum and it has about 22 wild species, 5 commercially cultivated: C. annuum (most cultivated pepper cultivars in the world), C. frutescens (the tabasco), C. chinense (habanero), C. baccatum (most common in South America) and C. pubescens (less known, mostly in Andean South America and the Central American highlands).
Pepper is native to Mexico, and grew in the wild as far back as 7,500 BC, and has been in cultivation since 3,500 BC. Columbus is said to be the one who introduced pepper/chile to Europe, and from there it spread eastward. And, it seems it was Vasco da Gama who brought pepper/chile to India, where perhaps because of the climate and soil, it has thrived. India is the biggest producer of chili in the world, exporting 35 tons/year, according to Reuters. In the US, the biggest chile producer is New Mexico. New Mexico State University in Las Cruces even has ‘The Chile Pepper Institute’ where, besides in-house research and graduate programs, annual conferences are held on various aspects of pepper (the one for 2006 was held in early February).
Now, the reason we feel its pungency is because an electron-poor area in capsaicins binds to receptor-proteins in the mouth lining and tongue. These are thermoreceptors, hence a burning feeling -- the result of calcium ions flowing from one cell to another. Pepper also releases endorphins, a neurotransmitter and a natural pain-killer, that attach to the same receptors as opiates, and produce a similar feeling. Eating hot food causes an endorphin-rush (sweating, some pain), a sense of euphoria, the kind felt by the joggers or those doing an exercise involving pain and stress.
Peppers are rich in Vitamin C, Vitamin A (in dried chilli), and beta-carotenes (red chillies), bioflavinoids and anti-oxidants. Bell pepper has 2x and red pepper 3x more Vitamin C than an orange (per unit weight). Capsaicin has a long history of medicinal use, dating back to the Mayans who used pepper/chile to treat asthma, sore throat, toothache, etc. Currently, it is an active ingredient in liniments (external application) used against aching muscles, arthritis and minor pains. It also has some anti-bacterial properties and is also a strong analgesic.
So, think about all this molecular gastronomy next time you go for really spicy food. Lot of folk-lore about what to do when it’s too hot, but remember, capsaicin is a fat-soluble substance (like oil): water won’t dissolve it, but would just distribute it to other parts of the mouth; bread and rice will however soak it up, milk may provide a coating. So, enjoy the meal.


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