The Scoville scale is the measurement of the pungency (spicy heat) of chili peppers or other spicy foods as reported in Scoville heat units (SHU), a function of capsaicin concentration. The scale is named after its creator, American pharmacist Wilbur Scoville. His method, devised in 1912, is known as the Scoville Organoleptic Test.
Unlike methods based on high-performance liquid chromatography, the Scoville scale is an empirical measurement dependent on the capsaicin sensitivity of testers and so is not a precise or accurate method to measure capsaicinoid concentration.
Scoville organoleptic test
In Scoville's method, an exact weight of dried pepper is dissolved in alcohol to extract the heat components (capsinoids), then diluted in a solution of sugar water. Increasing concentrations of the extracted capsinoids are given to a panel of five trained tasters, until a majority (at least three) can detect the heat in a dilution. The heat level is based on this dilution, rated in multiples of 100 SHU.
A weakness of the Scoville Organoleptic Test is its imprecision due to human subjectivity, depending on the taster's palate and their number of mouth heat receptors, which varies "greatly" among people. Another weakness is sensory fatigue: the palate is quickly desensitised to capsaicins after tasting a few samples within a short-time period. Results vary widely, ± 50%, between laboratories.
Since Scoville ratings are defined per unit of dry mass, comparison of ratings between products having different water content can be misleading. Typical fresh chile peppers have a water content around 90 percent, whereas, for example, Tabasco sauce has a water content of 95 percent. For law-enforcement-grade pepper spray, values from 500 thousand up to 5 million SHU have been mentioned, but the actual strength of the spray depends on the dilution, which could be a factor of 10.
The chiles with the highest rating on the Scoville scale exceed one million Scoville units, and include specimens of naga jolokia or bhut jolokia and its cultivar, the "Ghost chile", which does not have official cultivar status.
Numerical results for any specimen vary depending on its cultivation conditions and the uncertainty of the laboratory methods used to assess the capsaicinoid content. Pungency values for any pepper are variable, owing to expected variation within a species—easily by a factor of 10 or more—depending on seed lineage, climate (humidity is a big factor for the Bhut Jolokia; the Dorset Naga and the original Naga have quite different ratings), and even soil (this is especially true of habaneros). The inaccuracies described in the measurement methods above also contribute to the imprecision of these values.
ASTA pungency units
Since at least the 1980s, spice heat has been more precisely measured by a method that uses high performance liquid chromatography (HPLC). This identifies and measures the concentration of heat-producing chemicals. The measurements are used in a mathematical formula that weighs them according to their relative capacity to produce a sensation of heat. This method yields results, not in Scoville units, but in American Spice Trade Association (ASTA) pungency units. A measurement of one part capsaicin per million corresponds to about 15 Scoville units, and the published method says that ASTA pungency units can be multiplied by 15 and reported as Scoville units.
Scoville units are a measure for capsaicin content per unit of dry mass. This conversion is approximate, and spice experts Donna R. Tainter and Anthony T. Grenis say that there is consensus that it gives results about 20–40% lower than the actual Scoville method would have given.
- Wilbur Scoville profile on NNDB
- Periodic Table of Scoville Units Interactive Periodic Table of Scoville Units
- Scoville Scale/Scoville Heat Units Explanation at Tabasco web site
- Peter, KV, ed. (2001), Handbook of Herbs and Spices 1, CRC Press, p. 120, ISBN 0-8493-1217-5.
- The Journal of the American Pharmacists Association 1, 1912: 453–4.
- Kleiman, Dena (November 8, 1989). "Rating Hot Peppers: Mouth vs. Computer". The New York Times. Retrieved 2014-11-02.
- Peter, K. V. (2012). Handbook of Herbs and Spices. Elsevier Science. p. 127. ISBN 978-0-85709-567-1.
- Tainter, Donna R.; Anthony T. Grenis (2001). Spices and Seasonings. Wiley-IEEE. p. 30. ISBN 0-471-35575-5. "Interlab variation [for the original Scoville scale] could be as high as +/−50%. However, labs that run these procedures could generate reasonably repeatable results."
- Barry-Jester, Anna Maria (October 15, 2014). "Rating Chili Peppers On A Scale Of 1 To Oh Dear God I’m On Fire". FiveThirtyEight. Retrieved 2014-11-02.
- USDA nutrient database for Peppers, jalapeño, raw (92% water content); Peppers, hot chile, red, raw (88% water content); Red Tabasco sauce (95%)
- "Chemical hazards in law enforcement". The Police Policy Studies Council. Retrieved 2009-02-09. "Most law enforcement sprays have a pungency of 500,000 to 2 million SHU. One brand has sprays with 5.3 million SHU."
- "The Truth About Defensive Spray Heat". Sabre red. "Sabre Red = 10% OC @ 2,000,000 Scoville Heat Units. Thus, 90% of the formulation dilutes the 2,000,000 SHUs creating a Scoville Content of 200,000."
- "World’s hottest chilli grown in Grantham, Lincs". The Daily Telegraph (London). 2010-04-01. Retrieved 2010-04-24.
- "Grantham firm grows world's hottest chilli". UK: This is Lincolnshire. Retrieved 2010-04-24.
- "World's hottest pepper hits 2.2 million Scoville heat units". Los Angeles Times. December 26, 2013. Retrieved March 24, 2014.
- "Chile experts identify Trinidad Moruga Scorpion as world's hottest newspaper= The Daily Telegraph". UK. 2012-02-16.
- Dykes, Brett Michael (3 December 2010). "World’s hottest pepper is ‘hot enough to strip paint’". Yahoo! News. Retrieved 2010-12-03.
- "Tezpur/Naga Jolokia – The Hottest Chile?" (PDF). The Chile Pepper Institute Newsletter 11 (2) (The Chile Pepper Institute, New Mexico State University). 2000. p. 5. "...the Red Savina Habanero whose Scoville rating is around 555,000 Scoville Heat Units (SHU), the 'Naga Jolokia' possesses 855,000 SHU."
- "Grantham's Infinity chilli named hottest in world". BBC. 2011-02-18.
- Shaline L. Lopez (2007). "NMSU is home to the world's hottest chile pepper". Archived from the original on 2007-02-19. Retrieved 2007-02-21.
- "World's hottest chile pepper a mouthful for prof". CNN. AP. 23 February 2007. Archived from the original on 2007-03-22.
- Matthew Da Silva, "Aussies grow world's hottest chilli", Australian Geographic, 12 April 2011
- "UK's hottest commercially grown chilli pepper goes on sale".
- "World's hottest chile pepper discovered". American Society for Horticultural Science. Retrieved 2008-03-31.
- "Burning Questions" (PDF). The Chile Pepper Institute Newsletter 13 (3) (The Chile Pepper Institute, New Mexico State University). 2002. p. 7. "...'Red Savina' habanero...came in at a whopping 577,000 Scoville Heat Units."
- "Chile Pepper Heat Scoville Scale". About.com. Retrieved 2006-09-25.
- "Habanero White". Chile man. Retrieved 2011-09-21.
- "The Scoville Scale". HappyStove.com.
- Scoville Food Institute, Periodic Table of Scoville Units.
- "The Scoville Scale". The Scoville Scale For Peppers.
- "Scoville Scale Chart for Hot Sauce and Hot Peppers". Scott Roberts. Retrieved 2008-11-19.
- "Scoville hot sauce heat scale". HotSauce.com.
- Julius, David; Caterina, Michael J.; Schumacher, Mark A.; Tominaga, Makoto; Rosen, Tobias A.; Levine, Jon D. (1997). "The capsaicin receptor: a heat-activated ion channel in the pain pathway". Nature 389 (6653): 816–824. doi:10.1038/39807. ISSN 0028-0836. PMID 9349813. "Reported pungencies for pepper varieties (in Scoville units) are: Habanero (H),100,000–300,000; Thai green (T), 50,000–100,000; wax (W), 5,000–10,000; and Poblano verde (P), 1,000–1,500 (ref. 23)."
- Coon, Denise; Votava, Eric; Bosland, Paul W. (2008). "The Chile Cultivars of New Mexico State University" (PDF). Research Report 763. College of Agriculture and Home Economics, New Mexico State University. Retrieved 2013-08-09.
- Lillywhite, Jay M.; Simonsen, Jennifer E.; Uchanski, Mark E. (2013). "Spicy Pepper Consumption and Preferences in the United States.". HortTechnology 23 (6): 868–876. "Any pepper type with ≥ 1 SHU could be considered spicy. However, for this study, paprika (0–300 SHU), New Mexico long green or red chile (300–500 SHU), and poblano/ancho (≈1369 SHU) types were included as mild spicy peppers (Table 1)."
- Thomas DeBaggio, Thomas DeBaggio; Arthur O. Tucker, Arthur O. Tucker (2009). The Encyclopedia of Herbs: A Comprehensive Reference to Herbs of Flavor and Fragrance. Timber Press. p. 188. ISBN 978-1-60469-134-4. "...a bell pepper has 0 Scoville Heat Units and a rating of 0."
- Laratta, B; De Masi, L; Sarli, G; Pignone, D (2013). Lanteri, Sergo; Rotino, Giuseppe Leonardo, eds. "Hot Peppers for Happiness and Wellness: a Rich Source of Healthy and Biologically Active Compounds" (PDF). Breakthroughs in the Genetics and Breeding of Capsicum and Eggplant: Proceedigns of the XV EUCARPIA Meeting on Genetics and Breeding of Capsicum and Eggplant (Comitato per l'organizzazione degli eventi (COE) DISAFA, Università degli Studi di Torino): 233–240. ISBN 978-88-97239-16-1. "Scoville Heat Units (SHU), Referring pepper varieties...0, Sweet Bell"
- DeWitt, Dave; Bosland, Paul W. (2009). The Complete Chile Pepper Book. ISBN 978-0-88192-920-1.
- M.D. Collins et al., "Improved Method for Quantifying Capsaicinoids in Capsicum Using High-performance Liquid Chromatography". HortScience 30 137–139 (1995).
- Nwokem, C.O. et al. (2010). "Determination of Capsaicin Content and Pungency Level of Five Different Peppers Grown in Nigeria" (PDF). New York Science Journal 3: 9.
- Othman, Z.A. Al et al. (2011). "Determination of Capsaicin and Dihydrocapsaicin in Capsicum Fruit Samples using High Performance Liquid Chromatography". Molecules 16: 8919–8929. doi:10.3390/molecules16108919.