How long should onions be cooked for curry?

Onions need a minimum of 20–25 minutes on medium heat to properly caramelise. In this time water evaporates, sharp sulphur compounds break down, and Maillard browning creates over 50 complex flavour compounds. Most recipes underestimate this time. Correctly caramelised onions are deep golden-brown, almost jammy, and reduced by 60–70% in volume.

What does oil separation mean in Indian cooking?

Oil separation occurs when the water in the onion-tomato masala base has fully evaporated, releasing the absorbed fat back to the surface as small pools of oil around the edges of the pan. It is the most reliable indicator that the masala base is correctly cooked. Before oil separation, the base still contains raw moisture that produces flat, undercooked flavour in the final curry.

Why does my ginger garlic paste taste raw in the finished curry?

Ginger-garlic paste needs 3–4 minutes of direct cooking after adding to the onion base before the raw sharp compounds convert to milder aromatic ones. Adding it and immediately moving to the next step preserves the raw allicin from garlic and the sharp gingerols from ginger that produce harshness. Cook until the raw smell disappears and the paste darkens slightly.

Why Does My Curry Taste Raw and Pasty? | Food Failure Clinic

Q: Why does my curry taste raw and pasty?

Raw curry flavour comes from undercooked onions, tomatoes, and ginger-garlic paste. Raw onion contains harsh sulphur compounds. Undercooked tomato retains acidic malic acid rather than releasing its sweeter glutamate compounds. Undercooked garlic retains sharp allicin. Each needs specific cooking time — onions 20–25 minutes minimum, tomatoes 10–12 minutes after adding.

Q: How long should tomatoes be cooked in curry?

Tomatoes contain approximately 94% water by weight. They need a minimum of 10–12 minutes of active cooking after adding to fully evaporate this water and begin concentrating their glutamate and natural sugars into a thick paste. Cooking for only 5 minutes — as many recipes suggest — leaves too much moisture and produces a thin, acidic curry base.

The most common beginner failure

Why curry tastes raw — the chemistry of undercooked masala

A raw, pasty curry is almost always the result of one or two undercooked ingredients — and the most common culprits are onions and tomatoes. Raw onion contains sharp sulphur compounds that taste harsh and pungent. Undercooked tomato retains high concentrations of malic acid that create a thin, acidic sourness rather than the rounded umami sweetness of properly cooked tomato. Raw garlic contributes allicin — the same compound that makes raw garlic sharp on the palate. Any one of these undercooked produces a flat, harsh, "not quite right" result. All three together produce the distinctly raw, pasty flavour that most beginners recognise immediately.

🔍The Science

Why does onion need to be cooked so long — and what is actually happening?

Raw onion contains fructooligosaccharides — complex sugars — and sharp sulphur compounds including propanethial S-oxide (the compound that makes eyes water). Extended cooking over medium heat does three things: water evaporates, concentrating flavour; sulphur compounds break down into sweeter, milder molecules; and Maillard browning converts sugars and proteins into over 50 complex flavour compounds. A properly caramelised onion has lost 75% of its water weight and tastes completely different from a lightly sweated one. Most beginner recipes underestimate how long this takes — the minimum for correct caramelisation is 20–25 minutes on medium heat.

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The visual checkpoints — what correctly cooked masala looks like

Most recipes describe the end state of each stage but not the visual journey. Here is what to look for at each step:

Masala Base — Visual Checkpoint Guide

Onions — Stage 1 (5 min): Translucent, soft, still white. Not ready — sulphur compounds still present.

Onions — Stage 2 (12 min): Pale golden, significantly reduced in volume. Better but not enough Maillard browning yet.

Onions — Stage 3 (20–25 min): Deep golden-brown, almost jammy, volume reduced by 60–70%. This is correct.

After adding ginger-garlic paste: Cook 3–4 minutes until the raw smell disappears and the paste darkens slightly.

After adding tomatoes: Cook until all moisture has evaporated and oil visibly separates at the edges — minimum 10–12 minutes. The tomato should look almost paste-like, not wet.

After adding ground spices: Cook 2–3 minutes, stirring constantly. The masala should smell fragrant, not raw or floury.

✅The Fix

If your curry tastes raw after cooking

Return the curry base to the pan without protein or vegetables
Cook on medium-high heat, stirring frequently, for an additional 10–15 minutes
The raw taste is primarily from moisture — extended cooking drives off water and allows browning to continue
Add a tablespoon of oil if the base begins to stick — this is a sign the water has evaporated correctly
The masala is ready when oil visibly pools at the edges and the base has darkened by at least 2 shades

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The tomato problem — why most people add them too early or cook them too briefly

Tomatoes contain high water content — approximately 94% by weight. When added to a masala base, they dramatically drop the pan temperature and release this water into the cooking environment. Until all this water has evaporated, the pan temperature cannot rise high enough for Maillard browning to resume. Tomatoes need a minimum of 10–12 minutes of active cooking to evaporate their water and begin concentrating their glutamate and sugar content into the thick, rich paste that forms a correct curry base. Most beginner recipes say "cook for 5 minutes" — this is insufficient by half.

👤The test

The oil separation test — the most reliable indicator in Indian cooking

The single most reliable test for a correctly cooked masala base is oil separation — the moment when the oil or ghee that was absorbed into the onion-tomato mixture during cooking is released back to the surface as the water evaporates and the base becomes dry enough to stop holding the fat in emulsion. When you see small pools of orange-red oil appearing around the edges and on the surface of the masala, the base is correctly cooked. Before that moment, no matter how good the curry smells, the masala still contains enough raw moisture to produce a flat, undercooked flavour in the final dish.

Why are my spices sticking to the bottom?

Next problem

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Why Does My Curry Taste Raw and Pasty?

Why curry tastes raw — the chemistry of undercooked masala

The visual checkpoints — what correctly cooked masala looks like

The tomato problem — why most people add them too early or cook them too briefly

Frequently Asked Questions