Capsaicin
Also written capsaicinoids, capsaicin and dihydrocapsaicin, capsaicinoid
Quick answer
The compound that makes chillies hot, and the reason chilli heat behaves so unlike every other pungency in the spice cupboard: it is oily, it does not evaporate, and ordinary cooking removes only a part of it.
What it does
Capsaicin produces no taste and no smell. It stimulates the same nerve endings that report physical heat and abrasion, so the brain receives a signal indistinguishable from a burn — which is why the response is sweating, tears and a raised pulse rather than anything a taste receptor would produce. The sensation builds over roughly twenty seconds, peaks late, and fades slowly, and it accumulates across mouthfuls rather than resetting between them. Chillies also carry dihydrocapsaicin and several minor congeners in varying proportion, and the differing balance is part of why two chillies of similar measured strength can feel like a front-of-mouth sting and a slow throat heat respectively.
How it works
The physiological account, where one is established.
Capsaicin binds a receptor on sensory nerve fibres whose ordinary job is to detect noxious heat, and opens it at body temperature. The receptor is not a taste receptor and is not confined to the tongue: it is present wherever those nerve endings are, which is why capsaicin stings eyes and broken skin, and why cutting chillies without gloves has consequences hours later. Repeated exposure desensitises those endings, which is the basis both of acquired tolerance and of the topical pain preparations that use capsaicin deliberately.
How it behaves when cooked
Four properties of the molecule, and what they mean at the stove.
- Volatility
- low
- Fat solubility
- high
- Water solubility
- low
- Heat stability
- moderate
Every practical rule about chilli follows from these four properties. Because capsaicin is not volatile, it does not evaporate from the pot and is not lost from a pre-ground chilli the way aroma is. It does decline slowly in storage — losses of roughly a sixth to a quarter have been measured over months of warm or ambient storage — but far more slowly than the aroma, which is why chilli powder keeps most of its heat long after it has lost its fruit, and why whole-versus-ground matters far less for heat than for flavour. Because it is fat-soluble and barely water-soluble, water and beer move it around the mouth rather than removing it, while dairy, oil and coconut milk genuinely carry it away; the same solubility is why frying chilli in oil distributes heat evenly through a dish and why simmering it in a watery broth leaves the heat concentrated in the pieces. It is durable in heat without being indestructible: boiling and pressure cooking have been measured to remove between about one per cent and a third of it, and chilli fried in oil at 190 °C for ten minutes lost most of it. A dish that is too hot is therefore not rescued by cooking it longer — it is diluted, fattened or acidified.
Spices that carry it
Recorded on the compound rather than on each spice, so the two cannot disagree.
The wild progenitor of cultivated Capsicum annuum, and fiercely pungent: the plant evolved capsaicin to deter seed-destroying mammals, and birds, which disperse its seed, do not feel it.
Unusually, distributed through the thick flesh as well as the ribs, so deveining helps less here than in a thin-walled chilli and there is a great deal more flesh to deliver it.
Concentrated in the placental ribs rather than the flesh, which is why the Peruvian practice of deveining and blanching drops the heat so far — and why the pod Scoville figure does not describe the dish.
- Urfa biberMajor component
- Ají pancaContributing component
Deliberately low: the variety is grown and selected for colour rather than heat, which is the entire reason it is used by the tablespoon where a hotter chilli would be used by the pinch.
- PaprikaPresent in small amounts
Sweet paprika is made from cultivars bred down to almost no capsaicin. Hot paprika is the same species with the capsaicin left in, which is why the two are not interchangeable in either direction.
What cooking and processing were measured to do to it
Findings from studies in which this compound was followed through heat, fat, water, drying or storage. Each belongs to its study and its conditions.
Simmering and boiling · Decreases Capsaicin
Dried red pepper boiled for 10 or 20 min, or pressure cooked for 10 min, lost between 18 and 36 per cent of its capsaicin, the largest loss coming from pressure cooking. Neither red gram nor tamarind, nor the two together, changed the loss.
Conditions: in water · Boiling for 10 or 20 min; pressure cooking for 10 min · Dried red pepper (Capsicum annuum), alone and with red gram or tamarind
Capsaicin is more durable than most aroma compounds but it is not untouched by wet cooking: this study found a measurable part of it gone after minutes of boiling. Most of the heat remained.
What this does not show: Read in the abstract only. The cultivar and the form of the pepper are not stated there, and the fate of the lost capsaicin was not determined. Other studies of fresh peppers report smaller losses on boiling.
Measured on the spice
Simmering and boiling · Decreases Capsaicin
Poblano, Jalapeño, Serrano, Habanero
Across fresh Poblano, Chilaca, Caribe, Jalapeño, Serrano, Habanero and Manzano peppers, boiling at 96 °C under household conditions caused moderate losses of capsaicinoids, between 1.1 and 28.1 per cent. The proportions of capsaicin, dihydrocapsaicin and nordihydrocapsaicin to one another were similar in raw and cooked peppers.
Conditions: in water · 96 °C · Household boiling as done in Mexican cooking; eight pepper types
What this does not show: Read in the abstract only, which does not give the boiling time or say whether the missing capsaicinoids were destroyed or had moved into the water. The range across pepper types is wide.
Measured on the spice
Toasting and dry roasting · Increases Capsaicin
Poblano, Jalapeño, Serrano, Habanero
Grilling fresh Mexican peppers at 210 °C under household conditions raised their measured capsaicinoid content, by anything from 2.6 to 924.9 per cent depending on the pepper type, where boiling the same peppers had lowered it.
Conditions: in air · 210 °C · Household grilling as done in Mexican cooking
A charred fresh chilli is not made milder by the flame. Whether the rise reflects water driven out of the fruit, easier extraction from cooked tissue or both cannot be told from the published summary.
What this does not show: Read in the abstract only. The abstract does not say on what weight basis the contents were compared, and a grilled pepper has lost water, so the increase should not be read as capsaicinoid being made. The very wide range includes pepper types with almost none to begin with.
Measured on the spice
Frying and blooming in fat · Depends on conditions Capsaicin, pungency
Chilli powder fried in oil for 10 min gave up its capsaicinoids to the oil to an extent that depended on temperature. The oil held 14.8 mg/kg after frying at 130 °C, 20.9 at 150 °C, 19.4 at 170 °C and 7.4 at 190 °C, which the authors calculate as 73.5, 103.9, 96.4 and 36.8 per cent of what the powder contained. At 130 °C the release was incomplete; at 190 °C only about a third was recovered, which the authors attribute to serious loss of capsaicinoids at that temperature.
Conditions: in oil or fat · 130, 150, 170 and 190 °C · 10 min · Chilli powder fried in four times its weight of oil; proton NMR
Hot oil does carry chilli heat efficiently, but not at any temperature: in this preparation oil that was too cool left heat behind in the powder, and oil at 190 °C returned little more than a third of it.
What this does not show: One chilli powder, one oil and a single frying time of 10 min; a tempering lasts seconds and a poured chilli oil cools as it meets the chilli. A recovery above 100 per cent shows the size of the measurement error.
Measured on the spice
Frying and blooming in fat · Converts Capsaicin, Vanillin
The vanillin content of chilli oil rose steadily with frying temperature from 130 to 190 °C. Vanillin is a known thermal breakdown product of capsaicin, and the authors take its rise as confirmation that higher temperature drives the degradation of capsaicin in the oil.
Conditions: in oil or fat · 130 to 190 °C · 10 min
What this does not show: Vanillin can form from other constituents of chilli as well, and the study did not trace it to capsaicin directly. The amounts are far too small to be assumed perceptible.
Measured on the spice
Frying and blooming in fat · Converts Capsaicin, Vanillin, Methylnonenoic acid, Methylnonenamide, 9-Octadecenamide, N-Vanillyl-9-octadecenamide
Capsaicin decomposed by heat gives vanillin, methylnonenoic acid and methylnonenamide. Heated together with oleic acid, a fatty acid common in cooking oils, it also forms two products of reaction with the fat: 9-octadecenamide and N-vanillyl-9-octadecenamide.
Conditions: in oil or fat · High temperature; not stated in the published summary · Pure capsaicin alone and mixed with oleic acid; products identified by GC-MS
What this does not show: Read in the abstract only, which states neither the temperature nor how much of the capsaicin decomposed. Pure compound with a single fatty acid, not chilli in a cooking oil.
Measured on the pure compound
Acid and alkali · Depends on conditions Capsaicin
In a heated model system, capsaicinoid content fell faster at higher temperature whatever the starting concentration. Acidity mattered: at a fixed starting concentration the loss was slowest at neutral pH, faster under alkaline conditions and fastest under acidic ones. Higher starting concentrations slowed the rate of loss as heating went on.
Conditions: pH Acidic, neutral and alkaline compared · Model system; initial capsaicinoid concentrations of 200 to 1000 ppm
What this does not show: Read in the abstract only, which gives directions and no rates, temperatures or pH values. A model system, so it cannot be read as the behaviour of chilli in a vinegar sauce; a cooking study found tamarind made no difference to capsaicin loss.
Measured on the pure compound
Frying and blooming in fat · Retains Capsaicin, Capsanthin, colour, pungency
The carotenoids and capsaicinoids of chilli held up better under heat in an oil-based system, a hot pot base, than in a water-based one, chilli juice. Ultraviolet light significantly reduced both groups of compound in both systems, and storage at 4 °C significantly slowed their loss.
Conditions: in oil or fat · Hot pot base (oil system) compared with chilli juice (water system) under heat, light and storage
What this does not show: Read in the abstract only, which gives no figures or temperatures. The two systems differ in more than their medium, so the comparison is between two foods, not between oil and water alone.
Measured on the spice
Toasting and dry roasting · Decreases Capsaicin
Seeds from Korean dried red pepper held 36.50 mg of capsaicin per kilogram raw. Two minutes of roasting at 100 °C left this statistically unchanged at 32.57 mg/kg; two minutes at 200 °C lowered it significantly, to 19.47 mg/kg. Dihydrocapsaicin fell from 16.27 mg/kg raw to 12.60 at 100 °C and 9.40 at 200 °C.
Conditions: in air · 100 and 200 °C in a convection oven · 2 min · Seeds separated from Korean dried red pepper
What this does not show: Seeds separated from the fruit, which carry very little capsaicinoid to begin with; the flesh and the ground spice were not tested. One lot and one roasting time.
Measured on the spice
Crushing and cutting · Depends on conditions Capsaicin, pungency
Habanero, Carolina Reaper, Ghost pepper, Jalapeño, Cayenne pepper, Serrano
When the fruits of 21 chilli cultivars from four Capsicum species were dissected, the placenta, the pale tissue that carries the seeds, held the highest concentration of capsaicinoids in every species, followed by the flesh, with the seeds lowest in every cultivar. In Capsicum chinense the averages were 2600 mg per 100 g of dry weight in the placenta, 1738 in the flesh and 748.7 in the seeds. The seeds nevertheless made up about two thirds of the dry weight of the fruit. A separate study of Tabasco pepper found the placenta the tissue richest in capsaicinoid-related compounds, by a factor of about 35.
Conditions: Fruits of 21 cultivars cut by hand into pericarp, placenta and seeds; no heat applied
Cutting out the pale ribs and core removes the most concentrated source of heat in a chilli; the seeds come away with them, which is probably why the seeds are credited with it. In the hottest cultivars the flesh carries a great deal of capsaicinoid as well, so trimming reduces the heat without removing it.
What this does not show: Seeds dissected by hand had been lying against the placenta, so part of what was measured on them may have come from that contact. Concentrations are per dry weight; because seeds are dry and heavy, their share of a whole fruit’s total is larger than their concentration suggests.
Measured on the spice
Drying · Decreases Capsaicin, Dihydrocapsaicin, pungency
Every drying method lowered the capsaicin and dihydrocapsaicin content of chilli below that of the fresh fruit, and in every method the higher temperature lost more. The smallest loss, about 13 per cent, followed freeze-drying at 40 °C; the largest, about 45 per cent, followed hot air with 100 W of microwaves at 60 °C. Freeze-drying and vacuum drying did not differ significantly and kept the most.
Conditions: 40 and 60 °C · Freeze-drying, vacuum, hot air, and hot air with 50 or 100 W of microwaves
What this does not show: One cultivar, halved and deseeded, so that the inner tissue was exposed to the drying air. It conflicts with studies of whole pods in which hotter, faster drying left more capsaicinoid than slow drying; the material and the range of temperatures differ.
Measured on the spice
Drying · Depends on conditions Capsaicin, Capsanthin, Dihydrocapsaicin, pungency, colour
Whole chillies of two Guizhou varieties held significantly more capsaicin and dihydrocapsaicin after hot-air drying at 75 °C for 12 h than after five days in the sun or twelve days in the shade; the highest content, 1.71 mg/g, was in hot-air-dried Xianjiao. Capsanthin followed the same order, highest after hot air and lowest after shade-drying. The authors attribute the result to time: the slow methods leave enzymes active and oxidation running for days.
Conditions: in air · Hot air at 75 °C; sun at 25 to 33 °C; shade at 18 to 25 °C · 12 h; about 5 days; about 12 days · Two Guizhou varieties, whole fruit dried to about 7 per cent moisture
For a whole chilli, the long exposure of slow drying can cost more pigment and pungency than the heat of a quick one.
What this does not show: One season and three treatments that differ in several ways at once. The same study found shade-drying gave the richer aroma profile, so the ranking depends on what is valued. Conflicts with the finding on halved chillies that higher temperature lost more capsaicinoid.
Measured on the spice
Drying · Depends on conditions Capsaicin, pungency
In whole chillies dried in hot air, the measured capsaicin content was lowest after drying at 50 °C and highest after drying at 80 °C in two of three types: 1.77 per cent against 2.34 per cent in the long thin type and 2.33 per cent against 2.97 per cent in the millet type. The bullet type ranged only from 2.08 per cent at 70 °C to 2.24 per cent at 80 °C. The authors attribute the higher values at 80 °C to the much shorter drying time and to inactivation of peroxidase.
Conditions: in air · 50 to 80 °C · Whole fruit of three chilli types; capsaicin by a colorimetric method
What this does not show: The assay is colorimetric and less specific than chromatography, and its figures run higher than chromatographic values usually do. The explanation offered was not tested. Conflicts with the study of halved chillies in which the higher of two temperatures lost more capsaicinoid.
Measured on the spice
Decontamination · Retains Capsaicin, Capsanthin, hexanoic acid, tetramethylpyrazine, 1,3-di-tert-butylbenzene, microbial load, colour, pungency
Gamma irradiation of vacuum-packed Korean red pepper powder at 7 kGy reduced mesophilic bacteria and fungi effectively. Pungency was unchanged, by capsaicinoid content and by Scoville score, and the red colour did not differ significantly from the control by capsanthin content, ASTA units or Hunter values. A panel found no significant difference in pungent odour or off-odour. Instruments could nonetheless tell the doses apart: the headspace profiles separated at 0, 3, 5 and 7 kGy, with hexanoic acid and tetramethylpyrazine disappearing and 1,3-di-tert-butylbenzene appearing, a compound the authors trace to the irradiated packaging film migrating into the powder.
Conditions: Up to 7 kGy of gamma irradiation; powder vacuum-packed in a polyethylene/polypropylene bag
What this does not show: Read in the abstract only. A later study by another group reported that most panellists did detect an off-flavour in irradiated red pepper powder, so the sensory result is not settled. The packaging finding belongs to that film.
Measured on the spice
Decontamination · Retains Capsaicin, Capsanthin, microbial load, colour, pungency
Red pepper powder irradiated with gamma rays, electron beams or X-rays lost total aerobic microbes in proportion to the dose, and 6 kGy from any of the three sources reduced the population effectively. None of the three changed the capsaicinoid content, and neither capsanthin content nor Hunter colour values differed significantly from the control. A sensory panel found no significant difference in pungent odour or colour, but most panellists detected an off-flavour in the irradiated samples from every source.
Conditions: Gamma rays, electron beams and X-rays at doses up to 10 kGy
What this does not show: Read in the abstract only, which does not describe the off-flavour or the dose at which it appeared. An earlier study found no significant difference in off-odour at up to 7 kGy; the two used different panels and doses.
Measured on the spice
Decontamination · Depends on conditions Capsaicin, total carotenoids, N-methylpyrrole, dihydroactinidiolide, microbial load, colour
Electron-beam irradiation at 10 kGy left bacteria, yeasts and moulds almost undetectable in three paprika varieties. At 25 kGy the total carotenoid content had fallen by 16.91, 22.09 and 24.76 per cent in the three varieties. Capsaicin content did not change significantly with dose in two of them. New volatile compounds, N-methylpyrrole and dihydroactinidiolide, increased as the dose rose. The authors conclude that treatment up to 10 kGy was effective while preserving the properties they measured.
Conditions: Electron-beam irradiation at doses up to 25 kGy on three paprika varieties
What this does not show: Read in the abstract only. The carotenoid losses quoted are at 25 kGy, well above the dose the authors recommend; the abstract does not give the loss at 10 kGy.
Measured on the spice
Decontamination · Depends on conditions Capsaicin, total carotenoids, phenolic acids, microbial load, colour
In a traditional Himalayan paprika, gamma irradiation at 3 kGy gave a two-log reduction in bacterial count and a three-log reduction in yeasts and moulds, and in samples irradiated at 6 and 9 kGy no microbial growth was observed through nine months of storage. Measured capsaicinoids and phenolic acids increased significantly with irradiation, while carotenoids decreased significantly.
Conditions: Gamma irradiation at 3, 6 and 9 kGy, followed by storage under ambient conditions
What this does not show: Read in the abstract only, which gives no figures for the changes on irradiation itself. The abstract does not explain the apparent rise in capsaicinoids after irradiation, which should not be read as new capsaicinoid being formed.
Measured on the spice
Storage · Decreases Capsaicin, Capsanthin, dihydrocapsaicin, capsorubin, zeaxanthin, β-carotene, β-cryptoxanthin, pungency, colour
In a traditional Himalayan paprika stored under ambient conditions, total capsaicinoids and phenolic acids decreased significantly with storage, and so did the carotenoids. In the samples irradiated at 9 kGy, dihydrocapsaicin fell by 23.3 per cent and capsaicin by 21.0 per cent. Among the pigments, capsorubin fell least, by 19.2 per cent, against 29.9 per cent for capsanthin, 28.5 per cent for zeaxanthin and 29.5 per cent each for β-carotene and β-cryptoxanthin.
Conditions: Up to 9 months · Ambient conditions; figures are for samples irradiated at 9 kGy
In this paprika the pungent compounds were not indefinitely stable on the shelf: about a fifth was gone within the storage period, a smaller loss than that of the pigments but a real one.
What this does not show: Read in the abstract only. The percentages are given for the irradiated samples; those for the untreated control are not in the abstract, and neither are the packaging, temperature or humidity.
Measured on the spice
Packaging · Decreases Capsaicin, pungency, colour
Red chilli powder sealed in pouches and held at 40 °C for six months lost capsaicinoid content in every package, and the size of the loss depended on the film. It was greatest in polyethylene, 25.9 per cent, and least in a starch-based film plasticised with sorbitol, 15.7 per cent. The loss of extractable colour, measured by the ASTA method, followed the same order.
Conditions: 40 °C · 6 months · Heat-sealed starch-based film pouches compared with polyethylene
What this does not show: Read in the abstract only. An experimental film against one commercial polyethylene, at a temperature well above ordinary storage; capsaicinoids were measured by spectrophotometry, and the barrier properties of the films are not given there.
Measured on the spice
Not to be confused with
Compounds a reader is likely to take for this one, and why they differ.
Piperine
Black pepper is pungent through piperine, which is a different molecule acting on the same nerve population with roughly a hundredth of the potency. Quoting a Scoville figure for black pepper treats the two as one scale, which is why this catalogue records the pungency scale explicitly on every profile.
Capsanthin
The red pigment of the same fruit, and a completely separate compound. A chilli can be intensely red and not hot, or pale and ferocious; colour and heat are bred independently.
Safety
What the concern is. The dose, the population and the evidence level live on the spice profiles, which is where a reader with that question actually arrives.
Capsaicin is an irritant rather than a toxin at culinary exposures: the consequences of a large dose are pain, sweating and gastrointestinal upset rather than injury. The exposures that matter are the non-culinary ones — contact with eyes and broken skin when handling chillies, and concentrated extracts, which are a different proposition from the fruit. Individual tolerance varies enormously and is partly acquired.
Questions this page answers
- what is capsaicin
- what does capsaicin do
- which spices contain capsaicin
- what is capsaicinoids