Chilli and Heat: Where It Lives and How to Take It Back

Heat is not a taste

The tongue has receptors for sweet, salty, sour, bitter and savoury. It has none for heat. What capsaicin triggers is TRPV1, a pain receptor whose real job is detecting temperatures above about 43C. Your brain reads it as a burn.

That is why spicy food feels like it hurts pleasantly, why cooling the dish does not reduce the heat, and why you acclimatise with practice. It is a different system from the other five.

It lives in the white pith, not the seeds

Capsaicin concentrates in the placenta — the white pith the seeds are attached to. The seeds themselves carry almost none.

Deseeding does reduce heat, but only because the pith comes away with the seeds. To do it properly, scrape the white pith out with the tip of a knife. Carefully picking out seeds while leaving the pith accomplishes very little.

Water does not help

Capsaicin dissolves in fat, not in water. Drinking water spreads it around your mouth without removing any of it.

What does work:

• Dairy. Casein in milk binds capsaicin and carries it off. That is why India serves lassi and Thailand serves coconut milk alongside.
• Fat and oil, which capsaicin dissolves into.
• Sugar, which dampens the pain signal itself.
• Alcohol works in principle, but not at drinking strengths.

Chillies are not ranked on one axis

Sorting varieties by heat alone will ruin the dish.

• Kashmiri chilli is for colour. It is mild and deeply red, which is why three tablespoons go into rogan josh or vindaloo and the result is still gentle.
• Korean gochugaru brings aroma and a little sweetness. Substituted one-for-one for Kashmiri you get less colour and more perfume.
• Thai bird's eye is for heat. What two or three of them do in pad kra pao is hard to reproduce with anything milder.
• Dried and fresh chillies are different ingredients. Drying removes the green, grassy note and creates dried-fruit sweetness and smoke. Swapping one for the other is not substitution; it is a different addition.

Oil is what opens them

Capsaicin and the red pigments are both fat-soluble, so ground chilli slaked in water only half opens. Thirty seconds to a minute in oil turns the whole panful red and changes the aroma entirely (blooming spices).

A whole dried pod has a stage before the oil, and water is it

The line above is about ground chilli going into a pan. A whole dried pod is leather, and neither a mortar nor a blender makes anything of it until it has taken water back. So the order is water first and fat second — and the poor water-solubility that makes a soak a weak way to extract anything is exactly what lets a pod sit in it for twenty minutes without losing much.

Pozole Rojo runs all three media in order, and this page reads only its first step. Thirty seconds a side in a dry pan; then the warmed chillies "covered with hot water" for twenty minutes, until they are soft to the squeeze; then blended and pushed through a sieve; then poured into hot lard and fried five minutes "until it darkens and thickens. Skip this and the raw chilli taste never leaves." The dry pan changes the aroma, the water makes the pod grindable, and the fat opens what is inside it.

• The water stage is kept and the oil stage can be deleted. Kaeng Som seeds its chillies, soaks them twenty minutes and then squeezes them dry, and its paste "is never going to meet hot oil, so how fine it is is how much aroma you get" — with no fat anywhere in the dish, pounding is the whole of the opening (blooming spices prices that).
• What follows the water need not be oil either. Vindaloo blends the soaked chillies "using the 150ml of vinegar as the only liquid. Not a drop of water", because the acid has to be inside the paste; Papas Arrugadas's mojo rojo grinds them with vinegar and then works cold olive oil in "in a thin stream", so the fat arrives without ever being heated.
• And the soaking water is a tool, whose fate is a separate question. Vindaloo nails it into the step — "throw the soaking water away — it does not go into the paste" — while pozole puts a ladleful of it into the blender, having deseeded the pods first and sieved the purée afterwards. Soaking and rehydrating has the rule that decides which.

Enchiladas, Nasi Lemak's sambal, Khao Soi and Mi Rebus all take that same first step, and nasi lemak writes down what the second one is for: the paste is fried slowly "until fragrant and the red oil separates." The colour sat in the pod through the whole soak and came out in the pan.

But ground chilli burns in thirty seconds. That is why rogan josh drops the heat before the chilli goes in, and why malatang keeps its oil cool. Burnt chilli stays bitter through two hours of cooking.

The same thirty seconds applies to whole dried chillies, and there the cost of missing it is higher. Pozole Rojo warms its dried chillies in a dry pan for thirty seconds, and by the time they darken it is already too late: one scorched chilli makes the whole pot bitter. Toasting done on purpose, though, changes the aroma outright — the phrik pon in Leng Saep is dried chilli toasted in a pan and pounded, and it smells quite different from untoasted flakes. Even with gochugaru, a brief turn in a dry pan gets closer.

When you open them in oil, it is safer to measure the temperature. The chilli oil in Pai Huang Gua is made by bringing oil to about 160°C and pouring it over fine chilli flakes rather than putting the flakes into the pan — the oil then cools from that moment, so it never sits in the burning range.

The chilli's physical state is the dose

Put the last two facts together — the heat sits in the white pith, and it does not dissolve readily in water — and one practical conclusion falls out. How you put the chilli in is the dose control, and it only runs one way.

• Whole is a clock; split is committed. The scotch bonnet in Red Red lends aroma and can be lifted out while it is whole; split it and there is no going back. Fufu doses by time in exactly that way, adding the habanero whole and then removing it.
• How far you bruise it is the intermediate setting. Bruise the chillies in Pad Pak Boong Fai Daeng and the heat spreads through the dish; halve them instead and they can be picked out at the table.
• Heat and colour move separately. Chilli Crab deseeds its dried chillies: the colour stays and most of the heat goes.
• The surest control is not putting it in the pot. Capsaicin does not cook off, so once it is in there is no taking it out. Soup Curry is sold graded 1 to 10 because the cayenne is left to each person's bowl rather than the pot — one batch then feeds the chilli-inclined and everyone else.

When it has already gone too far

Capsaicin does not cook off. You cannot boil heat away, and there are only four moves.

• Add fat: coconut milk, cream, butter, yoghurt. The most reliable of the four.
• Add sugar. A teaspoon measurably lowers perceived heat.
• Add acid. Lime or vinegar does not reduce the heat but does distract from it.
• Add bulk — not water, but something absorbent like potato, tofu or rice. Water alone dilutes everything except the heat.

Which is why a too-hot tteokbokki is better served by sugar and fish cake than by a splash of water.

Heat is not one molecule

Every rule above is about capsaicin. The heat in mustard, wasabi and horseradish is a different molecule, and it reverses all four of those claims one by one — so a cook who knows only capsaicin cannot make a hot mustard sauce at all.

• It does not exist until you make it. Capsaicin is already sitting in the pith, but mustard's pungency is not present in an intact seed. Sinigrin and myrosinase live in separate cells and the heat is created the moment those cells break and the two meet.
• Water opens it, not oil. Capsaicin dissolves in fat and not in water; mustard needs water for the reaction to happen at all. And lukewarm water — boiling water destroys the enzyme, so mustard mixed with hot water is not hot.
• It fades as it cools and vanishes when boiled. Capsaicin's heat does not drop with temperature, but mustard's allyl isothiocyanate is volatile: an uncovered bowl is noticeably milder within the hour, and heat drives it off completely. It is also why the burn goes up your nose rather than sitting on your tongue.
• Acid stops the clock. Mixed and left about ten minutes, it peaks; vinegar added then locks it at that strength. Vinegar added at the start locks it in low.

That is why the mustard sauce in Dak-Hanmari nails the order into its steps, and Ilish Paturi handles the same molecule two opposite ways on one plate — the paste is mixed with cold water and sealed in a banana leaf to keep the aroma in, while the mustard oil is heated to smoking specifically to drive that aroma off.

The opposite case exists too. Dosa puts mustard seeds into hot oil until they pop. That destroys the enzyme, so no pungency survives at all and only a nutty aroma is left. Same seed, opposite handling, opposite result.

Count them and it does not stop at two

The contrast above closes at capsaicin against mustard, and there is something that belongs to neither. Spilanthol, in the mafana (paracress) leaf that goes into Madagascar's romazava, is not created by broken cells the way mustard's pungency is, and it does not burn the way capsaicin does. It tingles, numbs a little, and makes the mouth water — the plant is called the toothache plant for that reason.

Nor is it an isolated exception. The hydroxy-alpha-sanshool behind the buzz in mapo tofu and malatang is an alkylamide, and so is spilanthol. So "heat" on this page runs to at least three branches, and the alkylamide branch is closer to touch than to taste: not TRPV1 reading a temperature as pain, but tingling and a sense of vibration.

They are handled differently as a result. Sichuan pepper is a dried spice woken in oil, with the tingle out in front of the dish; mafana goes into the pot as a leaf and cooks for two minutes at the end. It is also why romazava is not a hot dish at all — the chilli stays out of the pot and arrives separately as sakay, which is the section above on "the surest control is not putting it in the pot", carried out exactly.

When "capsaicin does not dissolve in water" becomes a clock

Pikliz is scotch bonnet pickled in vinegar. There is almost no fat in that liquid, so the capsaicin leaves the pods very slowly — which is why a day-old jar is mild and a month-old jar is fierce. The rule above is first aid in your mouth; in a jar it is a clock.

Handling them

Since capsaicin does not rinse off with water, hands that have prepped chillies will still transfer it to your eyes after a wash. Rub oil into your hands first, then wash with soap. For any quantity, wear gloves.