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Pepper stand at Central Market in Houston, Texas, with Scoville scale
The Bhut jolokia ("ghost pepper") of Northeast India is considered to be a "very hot" pepper, having some 1 million SHU.[1]
The Naga Morich (also known as Dorset Naga) with around 1 million SHU[2] is primarily found in Bangladesh

The Scoville scale is a measurement of the pungency (spiciness or "heat") of chili peppers and other spicy foods, as recorded in Scoville Heat Units (SHU) based on the concentration of capsaicinoids, among which capsaicin is the predominant component.[3][4][5][6][7] The scale is named after its creator, American pharmacist Wilbur Scoville, whose 1912 method is known as the Scoville organoleptic test.[3][8] In the 21st century, high-performance liquid chromatography (HPLC) is used to quantify the capsaicinoid content as an indicator of pungency.[3][5][7] The most expedient method for estimating SHU is a subjective assessment derived from the capsaicinoid sensitivity by people experienced with eating hot chilis.[3][4]


Scoville organoleptic testEdit

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][9][10] 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.[3][9][10][1] The heat level is based on this dilution, rated in multiples of 100 SHU.[9]

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 chile pepper extract at which heat can be detected by a taste panel (Bosland et al., 2007)."[4][11]

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 people.[1][4] Another weakness is sensory fatigue;[1] the palate is quickly desensitized to capsaicinoids after tasting a few samples within a short time period.[9] Results vary widely (up to ± 50%) between laboratories.[10]

Pungency unitsEdit

The Red Savina pepper, a hot chili.[12]

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.[4][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."[4] HPLC results permit the measurement of a substance’s capsaicin capacity to produce perceived heat ("pungency"). This method yields results in American Spice Trade Association (ASTA) "pungency units", which are defined as one part capsaicin per million parts dried pepper mass.[5]

For parts per million (ppm) measurements: "Scoville Heat Units are calculated in parts per million of heat (ppm H) based on sample dry weight according to the following equation from ASTA (1985): ppm H = [Peak area of capsaicin + (0.82)(peak area of dihydrocapsaicin)](ppm standard)(ml acetonitrile) ÷ (Total capsaicin peak area of standard)(g sample). Conversion to Scoville Heat Units can be made by multiplying ppm H by a factor of 15"[5] (modified to a factor of 16 by others).[4]

Scoville ratingsEdit


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%.[13] For law-enforcement-grade pepper spray, values from 500,000 up to 5 million SHU have been reported,[1][14] but the actual strength of the spray depends on the dilution.[3]

Numerical results for any specimen vary depending on its cultivation conditions and the uncertainty of the laboratory methods used to assess the capsaicinoid content.[4] 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.[4][10]

Capsicum peppersEdit

Capsicum chili peppers are commonly used to add pungency in cuisines worldwide.[3][4] The range of pepper heat reflected by a Scoville score is from 100 or less (sweet peppers) to over 3 million (Pepper X) (table below; Scoville scales for individual chili peppers are in the respective linked article).

Scoville heat units Example peppers
800,000 to 3,200,000 Pepper X, Carolina Reaper, Dragon's Breath
350,000 to 800,000 Red savina, Chocolate habanero
100,000 to 350,000 Habanero, Scotch Bonnet
10,000 to 100,000 Malagueta pepper, Cayenne pepper
1,000 to 10,000 Guajillo pepper, Jalapeño
100 to 1,000 Banana pepper, Cubanelle
0 to 100 Bell pepper, Pimento


Capsaicin pharmacophore

The class of compounds causing pungency in plants like chili peppers is called capsaicinoids, which display a linear correlation between concentration and Scoville scale, and may vary in content during ripening.[15] Capsaicin is the major capsaicinoid in chili peppers.[5]

Scoville heat units Chemical
16,000,000,000 Resiniferatoxin
5,300,000,000 Tinyatoxin
16,000,000 Capsaicin, Dihydrocapsaicin[16]
9,200,000 Nonivamide[16]
9,100,000 Nordihydrocapsaicin[16]
8,600,000 Homocapsaicin, Homodihydrocapsaicin[16]
160,000 Shogaol
100,000 Piperine
60,000 Gingerol
16,000 Capsiate


  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. ^ a b c d e f g h i j Guzmán, I; Bosland, P. W (2017). "Sensory properties of chili pepper heat - and its importance to food quality and cultural preference" (PDF). Appetite. 117: 186–190. doi:10.1016/j.appet.2017.06.026. PMID 28662907.
  5. ^ a b c d e f Collins MD, Wasmund LM, Bosland PW (1995). "Improved method for quantifying capsaicinoids in Capsicum using high-performance liquid chromatography". HortScience. 30 (1): 137–139.CS1 maint: Uses authors parameter (link)
  6. ^ Peter, KV, ed. (2001), Handbook of Herbs and Spices, 1, CRC Press, p. 120, ISBN 978-0-8493-1217-5
  7. ^ a b Mazourek M, Pujar A, Borovsky Y, Paran I, Mueller L, Jahn MM (2009). "A Dynamic Interface for Capsaicinoid Systems Biology" (PDF). Plant Physiology, Bioinformatics. 150 (4): 1806–1821. doi:10.1104/pp.109.136549. PMC 2719146. PMID 19553373.
  8. ^ Scoville, Wilbur (May 1912). "Note on Capsicums". Journal of the American Pharmaceutical Association. 1 (5): 453–454. doi:10.1002/jps.3080010520.
  9. ^ a b c d Peter, K. V. (2012). Handbook of Herbs and Spices. Elsevier Science. p. 127. ISBN 978-0-85709-5671.
  10. ^ 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.
  11. ^ Stoica R, Moscovici M, Tomulescu C, Băbeanu N (2016). "Extraction and analytical methods of capsaicinoids - a review" (PDF). Scientific Bulletin. Series F. Biotechnologies. XX: 93–96. ISSN 2285-1364.
  12. ^ DeWitt, Dave; Bosland, Paul W. (2009). The Complete Chile Pepper Book. ISBN 978-0-88192-920-1.
  13. ^ USDA nutrient database for Peppers, jalapeño, raw (92% water content); Peppers, hot chile, red, raw (88% water content); Red Tabasco sauce (95%)
  14. ^ "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.
  15. ^ 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.
  16. ^ a b c d 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.

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