Two things sold under one name
A packet of red chilli powder is being asked to supply two entirely different qualities: pungency and colour. They come from unrelated compounds, they are produced in different parts of the fruit, and a chilli can have plenty of one and almost none of the other. Treating them as a single dial is the source of a great many disappointing dishes.
This is why cooks who care about the outcome keep at least two chillies in the cupboard, and why a recipe that specifies a variety is telling you something load-bearing rather than being precious about it.
Where the heat actually lives
Pungency comes from capsaicin and a family of closely related compounds. They are produced not in the flesh and not really in the seeds, despite the common belief, but in the white pith — the placental tissue that the seeds are attached to. Seeds taste hot mainly because they have been sitting against that tissue.
Capsaicin is not water-soluble, which has consequences all through cooking. It dissolves readily into fat and alcohol, which is why chilli bloomed in oil distributes its heat evenly through a dish and why dairy relieves a burning mouth while water merely moves it around. It is also remarkably stable, surviving heat, time and drying with little loss.
That stability is why an old jar of chilli powder can still be fiercely hot while smelling of almost nothing. The aromatic compounds, which are volatile, have left. The capsaicin, which is not, has stayed exactly where it was.
Colour is a separate chemistry with different weaknesses
The red comes from carotenoid pigments, chiefly capsanthin, concentrated in the skin and flesh. These are fat-soluble too, which is why chilli powder in hot oil releases a deep red that spreads through a gravy in a way that stirring the powder into water never achieves.
Unlike capsaicin, the pigments are fragile. They degrade under light, under heat and through oxidation, and the fading is visible — chilli powder that has gone from deep red to dull brick has lost pigment, and it will give a duller finish no matter how much of it you use. A clear jar on a sunny shelf accelerates this considerably.
Varieties bred for colour, of which the Kashmiri type is the best-known example, are relatively mild and heavily pigmented, so they let you build a red dish without making it painful. Varieties bred for heat are often comparatively pale. Combining the two in one dish, in whatever ratio suits you, is not a compromise — it is the point.
Whole, ground and soaked behave differently
Whole dried chillies keep both heat and aroma far longer, for the surface-area reasons that apply to every spice, and they can be used in ways a powder cannot. Fried whole in a tempering, a chilli contributes aroma and only a little heat, since the capsaicin mostly stays inside an intact fruit.
Soaking dried chillies in hot water and grinding them into a paste is the standard route to a smooth red gravy. It rehydrates the flesh, so the pigment disperses properly, and it gives a rounder, fruitier result than powder, which tends to read as sharper. Removing the pith before soaking is how you get the colour without the heat.
Ground chilli is the most convenient and the most fragile of the three. It burns almost instantly in properly hot oil because it is dry and finely divided, which is why it usually goes in with the heat lowered or off entirely, stirred through the fat for a few seconds rather than fried.
Buying with all this in mind
Colour is the one quality you can assess by eye through a clear packet, and it is the one that degrades fastest, so it is a reasonable proxy for how the powder has been stored. Bright and deep is good; dull and brownish means the pigment has already been going.
Heat is unknowable from the packet unless a variety is named, and even then the same variety varies with growing conditions and season. Start with less than you think, taste, and adjust — and keep in mind that heat perception builds over a meal, so a dish that seems mild at the first spoonful may not be by the fifth.
It is also worth keeping the two kinds in separate jars rather than blending them into a single house powder, tempting as that is. Once mixed you have lost the ability to adjust colour and heat independently, which was the entire advantage of buying two things in the first place, and you are back to one dial.
Common questions
Does removing seeds make a dish less hot?
A little, but less than expected, because the heat is mainly in the pith the seeds are attached to. Scraping out the white membrane makes a much bigger difference than picking out seeds.
Why is my gravy pale even with plenty of chilli powder?
Either the powder has lost its pigment, or it never met hot fat. The colour compounds are fat-soluble, so chilli stirred into a watery dish stays as suspended specks rather than dissolving into a red base.
Does cooking for longer reduce the heat?
Barely. Capsaicin is very stable and long cooking does not destroy it, though it does distribute it more evenly, which can make a dish feel less sharp. To reduce heat you have to dilute the dish or add fat and dairy.
Senior writer, Wah Taste
Mateo joined to cover everyday cooking, street food, spice & pantry and stayed for the awkward questions and thinks most subjects are more interesting once you know how they work.
