The Scoville scale is a measurement of pungency (spiciness or "heat") of chili peppers and other substances, recorded in Scoville heat units (SHU). It is based on the concentration of capsaicinoids, among which capsaicin is the predominant component.[3]

Pepper stand at Central Market in Houston, Texas, showing its peppers ranked on the Scoville scale
The ghost pepper of Northeast India is considered to be a "very hot" pepper, at about 1 million SHU.[1]
The Naga Morich, with around 1 million SHU,[2] is primarily found in Bangladesh.

The scale is named after its creator, American pharmacist Wilbur Scoville, whose 1912 method is known as the Scoville organoleptic test.[3][4] The Scoville organoleptic test is a subjective assessment derived from the capsaicinoid sensitivity by people experienced with eating hot chilis.[3]

An alternative method, high-performance liquid chromatography (HPLC), can be used to analytically quantify the capsaicinoid content as an indicator of pungency.[3][5][6]

Scoville organoleptic test edit

In the Scoville organoleptic test, an exact weight of dried pepper is dissolved in alcohol to extract the heat components (capsaicinoids), then diluted in a solution of sugar water.[3][7][8] Decreasing concentrations of the extracted capsaicinoids are given to a panel of five trained tasters, until a majority (at least three) can no longer detect the heat in a dilution.[1][3][7][8] The heat level is based on this dilution, rated in multiples of 100 SHU.[7]

Another source using subjective assessment stated: "Conventional methods used in determining the level of pungency or capsaicin concentration are using a panel of tasters (Scoville organoleptic test method). ... Pepper pungency is measured in Scoville heat units (SHU). This measurement is the highest dilution of a chili pepper extract at which heat can be detected by a taste panel."[5][9][10]

A weakness of the Scoville organoleptic test is its imprecision due to human subjectivity, depending on the taster's palate and number of mouth heat receptors, which vary widely among subjects.[1][9] Another shortcoming is sensory fatigue;[1] the palate is quickly desensitized to capsaicinoids after tasting a few samples within a short time period.[7] Results vary widely (up to ± 50%) between laboratories.[8]

Quantification by HPLC edit

The Red Savina pepper, a hot chili.[11]

Since the 1980s, spice heat has been assessed quantitatively by high-performance liquid chromatography (HPLC), which measures the concentration of heat-producing capsaicinoids, typically with capsaicin content as the main measure.[9][5] As stated in one review "the most reliable, rapid, and efficient method to identify and quantify capsaicinoids is HPLC; the results of which can be converted to Scoville heat units by multiplying the parts-per-million by 16."[9][a]

HPLC method gives results in American Spice Trade Association 1985 "pungency units", which are defined as one part capsaicin equivalent per million parts dried pepper mass. This "parts per million of heat" (ppmH) is found with the following calculation:[5]


Peak areas are calculated from HPLC traces of dry samples of the substance to be tested in 1 ml of acetonitrile. The standard used to calibrate the calculation is 1 gram of capsaicin. Scoville heat units are found by multiplying the ppmH value by a factor of 15.[5][a] By this definition of ppmH, spicy compounds other than the two most important capsaicinoids are ignored, despite the ability of HPLC to measure these other compounds at the same time.[5]

Scoville ratings edit

Considerations edit

Since Scoville ratings are defined per unit of dry mass, comparison of ratings between products having different water content can be misleading. For example, typical fresh chili peppers have a water content around 90%, whereas Tabasco sauce has a water content of 95%.[12] For law-enforcement-grade pepper spray, values from 500,000 up to 5 million SHU have been reported,[1][13] but the actual strength of the spray depends on the dilution.[3] This problem can be overcome by stating the water content along with the Scoville value. One way to do so is the "D-value", defined as total mass divided by dry mass.[14]

Numerical results for any specimen vary depending on its cultivation conditions and the uncertainty of the laboratory methods used to assess the capsaicinoid content.[9] Pungency values for any pepper are variable, owing to expected variation within a species, possibly by a factor of 10 or more, depending on seed lineage, climate and humidity, and soil composition supplying nutrients. The inaccuracies described in the measurement methods also contribute to the imprecision of these values.[9][8]

Pepper X, the world's hottest pepper as of 2023

Capsicum peppers edit

Capsicum chili peppers are commonly used to add pungency in cuisines worldwide.[3][9] The range of pepper heat reflected by a Scoville score is from 500 or less (sweet peppers) to over 2.6 million (Pepper X) (table below; Scoville scales for individual chili peppers are in the respective linked article). Some peppers such as the Guntur chilli and Rocoto are excluded from the list due to their very wide SHU range. Others such as Dragon's Breath and Chocolate 7-pot have not been officially verified.[15][16]

Scoville heat units Examples
2,693,000 Pepper X[17]
1,500,000–2,500,000 Carolina Reaper[18][19]
750,000–1,500,000 Trinidad Moruga Scorpion,[20] Naga Viper pepper,[21] Infinity chilli,[22] Ghost pepper[23]
350,000–750,000 Red savina habanero[24]
100,000–350,000 Habanero chili,[25] Scotch bonnet pepper[25]
50,000–100,000 Bird's eye chili (Thai chili pepper),[26] Malagueta pepper[26]
25,000–50,000 Tabasco pepper,[27] Cayenne pepper[28]
10,000–25,000 Serrano pepper,[29] Aleppo pepper,[30] Cheongyang chili pepper[31]
2,500–10,000 Jalapeño pepper,[32] Guajillo chili[33]
1,000–2,500 Poblano pepper[34][35]
500–1,000 Cubanelle,[36] Beaver Dam pepper[37]
0–500 Pimiento[38]
0 Bell pepper, Peperone crusco[39]

Capsaicinoids edit

The capsaicin "pharmacophore", the portion of the molecule that produces biological effects

The class of compounds causing pungency in plants such as chili peppers is called capsaicinoids, which display a linear correlation between concentration and Scoville scale, and may vary in content during ripening.[40] Capsaicin is the major capsaicinoid in chili peppers.[5]

The Scoville scale may be used to express the pungency of other, unrelated TRPV1 agonists, sometimes with extrapolation for much hotter compounds. One such substance is resiniferatoxin, an alkaloid present in the sap of some species of euphorbia plants (spurges). Since it is 1000 times as hot as capsaicin, it would have a Scoville scale rating of 16 billion.[41] In the table below, non-capsaicinoid compounds are italicized.

Scoville heat units Chemical Ref
16,000,000,000[b] Resiniferatoxin [42]
5,300,000,000[b] Tinyatoxin [43]
16,000,000 Capsaicin [44][45]
15,000,000 Dihydrocapsaicin [44]
9,200,000 Nonivamide [44]
9,100,000 Nordihydrocapsaicin [44][45]
8,600,000 Homocapsaicin, Homodihydrocapsaicin [44]
160,000 Shogaol [46]
150,000 Piperine [47]
60,000 Gingerol [46]

See also edit

Explanatory notes edit

  1. ^ a b Some sources such as Guzman[9] state a factor of 16 in line with the 16,000,000 SHU figure of pure capsaicin. However, Guzman cites the collins source[5] which clearly states 15 per ASTA.
  2. ^ a b Estimate; too strong to be used in human taste-testing.

References edit

  1. ^ a b c d e 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.
  2. ^ "Some Like It Hot: Dorset's Ultra-Hot Chillies". Archived from the original on 19 November 2012. Retrieved 25 August 2010.
  3. ^ a b c d e f g h Twilight Greenaway (10 January 2013). "How Hot is That Pepper? How Scientists Measure Spiciness"., US Smithsonian Institution. Retrieved 17 December 2017.
  4. ^ Scoville, Wilbur (May 1912). "Note on Capsicums". Journal of the American Pharmaceutical Association. 1 (5): 453–454. doi:10.1002/jps.3080010520.
  5. ^ a b c d e f g h Collins MD, Wasmund LM, Bosland PW (1995). "Improved method for quantifying capsaicinoids in Capsicum using high-performance liquid chromatography". HortScience. 30 (1): 137–139. doi:10.21273/HORTSCI.30.1.137.
  6. ^ Al Othman, Zeid Abdullah (2011). "Determination of Capsaicin and Dihydrocapsaicin in Capsicum Fruit Samples using High Performance Liquid Chromatography". Molecules. 16 (10): 8920. doi:10.3390/molecules16108919. PMC 6264681. PMID 22024959.
  7. ^ a b c d Peter, K. V. (2012). Handbook of Herbs and Spices. Elsevier Science. p. 127. ISBN 978-0-85709-5671.
  8. ^ a b c d Tainter, Donna R.; Anthony T. Grenis (2001). Spices and Seasonings. Wiley-IEEE. p. 30. ISBN 978-0-471-35575-5. Interlab variation [for the original Scoville scale] could be as high as +/−50%. However, labs that run these procedures could generate reasonably repeatable results.
  9. ^ a b c d e f g h Guzmán, I; Bosland, P. W (2017). "Sensory properties of chili pepper heat - and its importance to food quality and cultural preference". Appetite. 117: 186–190. doi:10.1016/j.appet.2017.06.026. PMID 28662907.
  10. ^ Stoica R, Moscovici M, Tomulescu C, Băbeanu N (2016). "Extraction and analytical methods of capsaicinoids - a review" (PDF). Scientific Bulletin. Series F. Biotechnologies. XX: 93–140. ISSN 2285-1364. S2CID 38430045. Archived from the original (PDF) on 2018-08-11.
  11. ^ DeWitt, Dave; Bosland, Paul W. (2009). The Complete Chile Pepper Book. Timber Press. ISBN 978-0-88192-920-1.
  12. ^ USDA nutrient database for Peppers, jalapeño, raw (92% water content); Peppers, hot chile, red, raw (88% water content); Red Tabasco sauce (95%)
  13. ^ "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.
  14. ^ "Let's Get Technical: The Limitations of the Scoville Scale". Josh's Jungle. 22 April 2017.
  15. ^ Mike Hultquist (23 February 2018). "Pepper X – Latest News and Information". Chili Pepper Madness. Retrieved 21 January 2019.
  16. ^ Ligaya Mishan (August 18, 2022). "How the Chile Became Hot". The New York Times. Retrieved September 1, 2022. Carolina Reaper, known to reach as many as 2.2 million S.H.U.s — more potent than some pepper sprays — and certified by Guinness World Records as the hottest chile on earth.
  17. ^ "Pepper X, Hottest chilli pepper". Guinness World Records Ltd. 2023. Retrieved 16 October 2023.
  18. ^ Hallock, Betty (December 26, 2013). "World's hottest pepper hits 2.2 million Scoville heat units". Los Angeles Times.
  19. ^ "Hottest chilli pepper (2017)". Guinness World Records. Archived from the original on January 28, 2023. Retrieved October 16, 2023.
  20. ^ "Chile experts identify Trinidad Moruga Scorpion as world's hottest". The Daily Telegraph. UK. 2012-02-16.
  21. ^ Dykes, Brett Michael (3 December 2010). "World's hottest pepper is 'hot enough to strip paint'". Yahoo! News. Retrieved 3 December 2010.
  22. ^ "Grantham's Infinity chilli named hottest in world". BBC News. 2011-02-18.
  23. ^ Lopez, Shaline L. (2007). "NMSU is home to the world's hottest chile pepper". New Mexico State University. Archived from the original on 2007-02-19. Retrieved 2007-02-21.
  24. ^ "World's hottest chile pepper discovered". American Society for Horticultural Science. Archived from the original on 2021-11-15. Retrieved 2008-03-31.
  25. ^ a b "Chile Pepper Heat Scoville Scale". Archived from the original on 2012-02-26. Retrieved 2006-09-25.
  26. ^ a b "Scoville Scale Chart for Hot Sauce and Hot Peppers". Scott Roberts. Retrieved 2008-11-19.
  27. ^ Andrews, Jean (1995). Peppers: the Domesticated Capsicums (illustrated ed.). University of Texas Press. p. 58. ISBN 9780292704671.
  28. ^ "Database of Chilli Pepper Varieties". The Chileman. Retrieved November 9, 2017.
  29. ^ "Types of hot peppers". Retrieved 19 May 2022.
  30. ^ "Pepper Heat Ratings in Scoville Units". Penzeys Spices. Archived from the original on 2010-02-27. Retrieved 2010-10-20.
  31. ^ Crawford, Matthew C. (5 September 2014). "Hot pepper town swept by heat wave". The Korea Herald. Retrieved 9 January 2017.
  32. ^ González-Zamora, A; Sierra-Campos, E; Luna-Ortega, J. G; Pérez-Morales, R; Rodríguez Ortiz, J. C; García-Hernández, J. L (2013). "Characterization of different Capsicum varieties by evaluation of their capsaicinoids content by high performance liquid chromatography, determination of pungency and effect of high temperature". Molecules. 18 (11): 13471–86. doi:10.3390/molecules181113471. PMC 6269802. PMID 24184818.
  33. ^ Bray, Matt (22 November 2014). "Guajillo pepper: The sweet side of spice". Retrieved 4 September 2018.
  34. ^ Lillywhite, Jay M.; Simonsen, Jennifer E.; Uchanski, Mark E. (2013). "Spicy Pepper Consumption and Preferences in the United States". HortTechnology. 23 (6): 868–876. doi:10.21273/HORTTECH.23.6.868. 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).
  35. ^ 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. Bibcode:1997Natur.389..816C. doi:10.1038/39807. ISSN 0028-0836. PMID 9349813. S2CID 7970319. 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).
  36. ^ "Scoville Scale – Scott Roberts Hot Sauce, BBQ and Spicy Food Blog".
  37. ^ "Beaver Dam Pepper: Northern Spice". 6 October 2015.
  38. ^ Thomas R. Koballa; Lee Meadows; Elizabeth C. Doster; David F. Jackson. (1995). "Hot Peppers to Hurricanes: New Ways to Measure". Science Scope. National Science Teachers Association. 19 (2): 39. JSTOR 43179500.
  39. ^ "Peperone Di Senise: Basilicata's Sweet Treasure". 17 August 2019. Retrieved 17 September 2020.
  40. ^ Nagy, Z; Daood, H; Ambrózy, Z; Helyes, L (2015). "Determination of Polyphenols, Capsaicinoids, and Vitamin C in New Hybrids of Chili Peppers". Journal of Analytical Methods in Chemistry. 2015: 1–10. doi:10.1155/2015/102125. PMC 4606152. PMID 26495153.
  41. ^ Atala, Anthony; Slade, Debra (2003). Bladder Disease. Washington, DC: National Bladder Foundation. p. 361.
  42. ^ Ellsworth, Pamela; Wein, Alan J. (2009). Questions and Answers about Overactive Bladder. Jones & Bartlett Learning. pp. 97–100. ISBN 978-1449631130.
  43. ^ Premkumar, Louis S. (2014-06-13). "Transient Receptor Potential Channels as Targets for Phytochemicals". ACS Chemical Neuroscience. 5 (11): 1117–1130. doi:10.1021/cn500094a. ISSN 1948-7193. PMC 4240255. PMID 24926802.
  44. ^ a b c d e Govindarajan, Sathyanarayana (1991). "Capsicum — Production, Technology, Chemistry, and Quality. Part V. Impact on Physiology, Pharmacology, Nutrition, and Metabolism; Structure, Pungency, Pain, and Desensitization Sequences". Critical Reviews in Food Science and Nutrition. 29 (6): 435–474. doi:10.1080/10408399109527536. PMID 2039598.
  45. ^ a b O'Keefe, James H.; DiNicolantonio, James J.; McCarty, Mark F. (2015-06-01). "Capsaicin may have important potential for promoting vascular and metabolic health". Open Heart. 2 (1): e000262. doi:10.1136/openhrt-2015-000262. ISSN 2053-3624. PMC 4477151. PMID 26113985.
  46. ^ a b Compton, Richard G.; Batchelor-McAuley, Christopher; Ngamchuea, Kamonwad; Chaisiwamongkhol, Korbua (2016-10-31). "Electrochemical detection and quantification of gingerol species in ginger (Zingiber officinale) using multiwalled carbon nanotube modified electrodes". Analyst. 141 (22): 6321–6328. Bibcode:2016Ana...141.6321C. doi:10.1039/C6AN02254E. ISSN 1364-5528. PMID 27774555. S2CID 40241982.
  47. ^ Mangathayaru, K. (2013). Pharmacognosy: An Indian perspective. Pearson Education India. p. 274. ISBN 9789332520264.