Blooming Spices: Why Aromatics Go into Fat First

Aroma dissolves in fat, not water

Most of what you smell in a spice — terpenes, capsaicin, curcumin — is fat-soluble. Stirred into water only some of it comes out; hit with hot oil, far more is extracted and it spreads through the whole dish.

That is why Indian, Thai and Middle Eastern cooking almost always starts by frying spice in fat. Butter Chicken, Biryani and Chana Masala all do.

Mustard runs the other way

One spice does not obey the fat-soluble premise. Mustard's pungency does not exist in the seed at all: sinigrin and the enzyme myrosinase have to meet water to make it. And the compound they make is destroyed by heat.

Saffron does not obey it either, for a different reason. Both the crocin that carries its colour and the safranal that carries its aroma dissolve readily in water, so the threads are steeped rather than fried — paella puts them in warm stock at the start of the recipe, and thrown into hot oil instead they colour in patches and give up about half their scent. So "aroma goes into fat" is a rule with two named exceptions, and both of them are answered by liquid rather than by oil.

So the same seed gives two opposite results.

• Masala Dosa fries mustard seed in hot oil until it pops. The enzyme is destroyed, so there is no pungency at all and what is left is a nutty aroma.
• Ilish Paturi grinds mustard in cold water and never heats it. The pungency arrives intact.
• The mustard sauce in Dak-hanmari is mustard powder let down with water at about 40C, left ten minutes, and only then given vinegar. Boiling water kills the enzyme and the sauce is not hot at all; vinegar added early freezes it at whatever strength it had reached.

An aroma opened by water rather than fat. It is also volatile in a way capsaicin is not: an open bowl loses much of it within the hour, and boiling removes it outright.

When there is no fat in the dish at all

The two exceptions above are ingredients that sit on the other side of the premise. A different case leaves the premise perfectly true and gives you nothing to use it with: a dish with no oil, no butter and no coconut milk anywhere in it. Frying the spice is not a step being skipped — there is no fat to fry it in.

Kaeng som says so outright. The curries beside it all open by frying a paste in fat — green curry cracks coconut cream and fries the paste in the oil that separates, laksa fries its rempah until the oil breaks out — and "kaeng som has neither coconut milk nor oil, so that line simply does not apply to it." What is left is the dial the garlic sections below are also about, how far the cells are broken: "with no fat to do the extracting, the only variable left is surface area, so this paste is worked until no fibre is visible at all." A blender does it badly, because blades cut where crushing opens cells.

Tom yum answers the same problem from the other end of that dial. It is fat-free and sour too, and rather than grinding its aromatics it bruises lemongrass, galangal and kaffir lime leaf whole and infuses them in the broth, to be fished out before serving (fresh herbs). Ground until no fibre shows, or bruised in lengths: one dial, set at its two ends, by two fat-free Thai soups.

What the fat would also have done is round things off, and that bill arrives as well. Som tam puts it plainly — everything in it is water-soluble and arrives at full strength at once, which is why the recipe is a ratio you taste to rather than a method. Heat does the same: with no fat to dissolve into and spread it, capsaicin stays on the chilli particles suspended in the broth, so the same weight of chilli reads sharper and unevenly, spoonful to spoonful (chilli and heat).

The same shells, and the medium decides which half of them you get

The premise sorts compounds, and an ingredient is a bag of several that need not agree. A prawn shell is a plain example of it, and it is put to work three different ways.

• Tom yum puts them in water. Heads and shells are fried briefly and then simmered into the stock, and what a clear sour soup wants is the savour. That page states the split: "the orange that bleeds out of a fried shell is a carotenoid and dissolves in fat; the savour is water-soluble and comes out into a simmer."
• Poo pad pong curry puts them in oil. "The shells give the sauce, so fry a handful of prawn shells in the oil first to make some of it back" — that sauce is built on a coloured, perfumed oil, and the shells are where it comes from.
• Kaeng som puts them in neither. Its prawn version pounds shells and heads into the paste, so nothing is extracted into anything and all of it stays in the bowl.

So the question a recipe is answering is not whether an ingredient is fat-soluble. It is which of the things it carries this dish has a use for, and the medium is how that choice gets made.

Whole spices first, ground spices later

• Whole (cumin seed, cardamom, cinnamon, cloves, bay): into the hot oil first. Twenty to thirty seconds and the aroma bursts out.
• Ground (chilli powder, turmeric, ground coriander, garam masala): burns far more easily. These go in later, just before the liquid.

Ground spice can survive in the pan for roughly thirty seconds. After that it turns bitter. If you are unsure, add a splash of liquid first to bring the temperature down.

Sichuan pepper is whole, and it still goes last

The Sichuan dishes cite this section by name and then do the opposite of it. Huoguo writes "do not add the peppercorns early. Whole spices need time to give up their aroma, but Sichuan peppercorn is the reverse, so the last minute is exact." Mala xiang guo goes a step further and folds them in off the heat, "with residual heat only". Dan dan noodles never puts them in oil at all — a minute in a dry pan, ground, and scattered on at the end. All three are whole spices by the row above, and all three are placed later than the ground ones.

Those two rows sort by how fast a spice burns, and underneath them sits an assumption that step 2 of the next section states outright: the job of the fry is to move the aroma into the fat. Sichuan pepper's payload is not an aroma. Chilli and heat files hydroxy-alpha-sanshool as an alkylamide whose sensation is "closer to touch than to taste — not TRPV1 reading a temperature as pain, but tingling and a sense of vibration", and the dishes supply the consequence. Huoguo's step says the numbing compounds are heat-sensitive, so "fry them long and the ma disappears, leaving just bitterness"; mala xiang guo says the same of a live flame. There is nothing here for the fat to carry, and going in first means sitting in the pan through everything that comes after.

So the same peppercorn is placed almost anywhere, and what decides it is which half of the spice the dish is after.

• The tingle, kept. Kung pao chicken gives it thirty seconds in a pool of moderate oil, with the burner dropped on purpose between two high-heat stages; malatang blooms it with the doubanjiang over low heat; huoguo waits for the last minute; mala xiang guo kills the flame first; dan dan noodles keeps it out of the oil altogether.
• The scent, with the tingle given up. Huiguorou puts Sichuan pepper into cold water with the spring onion, ginger and wine, simmers the pork in it for twenty-five to thirty minutes, then lifts the meat out and leaves the spice behind. That is the ordinary rule above running exactly as written, on the half of the spice that survives it — a poaching liquid you are going to throw away is not where anyone is keeping a buzz.
• Neither, and no pan at all. Paocai drops it into a cold 5% brine with the chillies, ginger and star anise and gives it days.

Chilli and heat calls it "a dried spice woken in oil, with the tingle out in front of the dish", and that stays true — oil is where it is woken. What that sentence does not settle is when, and the answer is the far end of the pan rather than the near one.

The order exists for a reason

1. Heat the fat. 2. Whole spices — move their aroma into the fat. 3. Onion — the slowest. Drive off water, develop sweetness. 4. Garlic and ginger — they burn much faster than onion. In once the onion is half done. 5. Ground spices — thirty seconds. 6. Tomato paste or liquid — drops the temperature and lifts the fond.

Add garlic with the onion and it burns before the onion is cooked. Getting just this order right changes a curry noticeably.

The dish that deletes step 1

Ethiopian Doro Wat puts a kilo of finely chopped red onion into a dry pot with no fat at all and cooks it for close to an hour. The butter arrives only once the onion has collapsed.

The principle still holds — the butter is late because it goes in with the berbere. What makes that order work is that the onion here is not an aromatic, it is the body of the sauce. No flour, no tomato, no cream, so driving the water out of the onion without fat is how the thickness gets built.

The thirty-second rule for ground spice is an exception in the same dish. Berbere goes in with the butter and cooks far longer, because after an hour of dry onion the pan is nowhere near the temperature that would burn it.

The same order, run at the other end

Deleting step 1 still leaves the sequence pointing forward. A tadka turns it round: the fat is heated, the spice is bloomed in it exactly as above, and the whole pan is then poured over a dish that is already finished. Dal simmers its lentils soft with nothing but turmeric and gets almost all of its aroma in the last ten seconds; Rasam says it in those words — "the tadka is not a last ingredient, it is a last cooking step."

This is not the finishing list at the end of this guide. Those are things added without heat, because heat is what would destroy them. A tadka is a complete blooming step at frying temperature; only its position has moved. It exists because two facts pull against each other — aroma has to meet hot fat to come out at all, and once it is out it is volatile. Frying the spice answers the first; frying it last answers the second. It is why rasam is taken off the moment it froths instead of being boiled: a minute at a hard boil takes away much of the tadka it has just been given.

Hainanese Chicken Rice moves it further out again. The hot oil is poured over raw minced ginger and spring onion in a bowl, so that aroma never goes near the pot at all.

And how coarsely you grind is a separate dial from how recently. Rasam cracks its pepper coarse on purpose: ground fine it has far more surface area, gives its aroma up faster, and disperses through the broth as a muddy dust, while coarse fragments are still releasing at the table. The storage section at the end of this guide says to grind as you need it — grind size is the other half of the same fact.

Tomato paste is something you fry, too

Stirred straight into liquid, tomato paste keeps a sharp raw acidity. Fried in fat for a minute or two, until it darkens and starts to stick, it turns sweet and savoury. It is why the sauces in Pique Macho and Iraqi Dolma look as deep as they do.

A wet spice paste: fry it until the oil breaks out

Across Southeast Asia this is not a step, it is the opening of the whole dish. A ground paste of garlic, shallot, chilli and spice — bumbu in Indonesia, rempah in Malaysia — goes into oil, and what tells you it is done is not a clock, it is the oil. Once enough water has left the paste, the oil you added separates back out onto the surface. Add the liquid before that and a raw garlic smell and a hard spice edge stay in the dish to the end.

Rendang, Rawon, Laksa, Mee Rebus and Ikan Pepes are all decided at that one step. While the paste is wet the pan cannot get past 100C, so the oil breaking out is really the pan telling you the water has gone.

Garlic is three different ingredients depending on heat

• Low heat, aroma only: sweet and mild. This is what Aglio e Olio is aiming at — browning it is a failure.
• Medium, browned: nutty and much deeper.
• Burnt: bitter, and irreversible.

Same clove, three outcomes. See Heat control.

Garlic has a second axis: how it was cut

Those three are the heat axis. There is another that uses no heat at all.

An intact clove contains no pungency whatsoever. Alliin and the enzyme alliinase sit in separate cells and only meet when the cell walls rupture, which is when allicin is made. So one clove gives you

• sliced — fewest cells broken, mildest;
• chopped — in between;
• crushed — strongest.

Three different strengths, and the reaction peaks at around ten minutes. Chopping the garlic while the cucumber salts in Pai Huang Gua is arithmetic, not a work order.

And a position where the clove never joins the dish

All three above share a premise: that the broken garlic goes in. A further position on the same axis drops it — the cut face is rubbed over a surface and the clove is thrown away. What does the cutting there is not a knife but the surface being rubbed, and the only cells that rupture are the outermost layer of the cut face. Fewer than any of the three.

Which means the dose is set by that surface rather than by how many cloves. Gratin dauphinois rubs the inside of the dish and writes down why: "chopped garlic catches in dairy over an hour and leaves bitterness and a texture you notice. Only the scent is wanted." Salade niçoise rubs a wide dish and lays the lettuce on it. Both of those rub the vessel; Bruschetta rubs the food, where a warm, dry, rough crust is the grater.

It also lands somewhere else on the clock. Allicin made by rubbing is made on the surface seconds before it is eaten, so it has no time to climb the ten-minute curve — which is why bruschetta can use both ends of that curve on one plate, giving the garlic minced into the tomatoes exactly those ten minutes and the garlic on the bread a few seconds.

Aromas that go in at the end

Anything heat-fragile is added off the heat.

• Fresh herbs (coriander, basil, parsley, dill): long cooking drives the aroma off.
• Toasted sesame oil: a finishing oil, not a cooking one.
• Garam masala: often added a second time at the end, even in India.
• Black pepper: ground fresh. Pre-ground pepper has almost no aroma left.

Peppercorns also go in whole sometimes, and then they are an ingredient rather than a seasoning. Norwegian Fårikål layers them in as they are. Ground, the heat spreads through the whole broth and buries the sweetness of the cabbage; whole, it only arrives when you bite one. The same pepper, either as the background of a broth or as an occasional point.

Storage

Ground spices lose most of their aroma in six to twelve months; whole ones keep two or three years. Grinding as you need it makes more difference than buying new spice — buy whole and grind. It matters most where the aroma is the dish, like the Sichuan pepper in Mapo Tofu.