Why Mustard Oil Is the Only Oil for Fish Cooking in India

Ask a Bengali cook what oil they use for fish. Ask a Punjabi cook what they marinate their machhi in. Ask a Bihari cook what goes into their fish curry. The answer is always the same: mustard oil.

This is not coincidence. The pairing of mustard oil and fish is one of the most deliberate flavour combinations in Indian cooking — developed over centuries in the river-rich regions of Bengal, Bihar, Assam, and Odisha, and in the fishing communities of Punjab and UP.

Here's why mustard oil and fish belong together, and how to use this combination properly.

The Flavour Chemistry

Mustard oil contains allyl isothiocyanate — the compound responsible for its characteristic pungency. Fish contains trimethylamine oxide (TMAO), which breaks down to trimethylamine (TMA) — the compound responsible for the "fishy" smell.

When mustard oil is applied to fish (in a marinade or during cooking), the allyl isothiocyanate reacts with and neutralises trimethylamine. This is why fish marinated in mustard oil smells less "fishy" and tastes cleaner than fish cooked in neutral oil.

This is not folk wisdom — it's chemistry. The same principle is why mustard is traditionally served with fish in European cuisine.

Additionally, mustard oil's pungency complements the natural richness of fish. The sharpness of the oil cuts through the fattiness of fish like hilsa, mackerel, and rohu, creating a balance that neutral oils cannot achieve.

Regional Fish Traditions

Bengal: The Mustard Oil Capital of Fish Cooking

Bengali cuisine has the most sophisticated tradition of mustard oil and fish cooking in India. The combination appears in dozens of preparations:

Shorshe ilish (hilsa in mustard sauce): The most celebrated Bengali fish dish. Hilsa (ilish) is marinated in mustard oil, then cooked in a sauce of ground mustard seeds, green chillies, and more mustard oil. The dish is essentially a meditation on mustard in all its forms.

Doi maach (fish in yoghurt): Mustard oil for frying the fish and for the base of the sauce.

Chingri malai curry (prawn in coconut milk): Mustard oil for the initial frying of prawns before the coconut milk is added.

Macher jhol (everyday fish curry): Mustard oil is the only acceptable cooking medium.

The Bengali rule: fish is always fried in mustard oil before being added to any curry. This step — called "bhaja" — creates a flavour foundation that no other oil can replicate.

Punjab: Amritsari Machhi

Amritsari machhi is perhaps the most famous North Indian fish preparation. The marinade is built around mustard oil:

• Fish (typically rohu or singhara) marinated in mustard oil, ginger-garlic paste, ajwain, red chilli, and besan
• Deep-fried in mustard oil
• Served with mint chutney and laccha pyaz

The mustard oil in the marinade penetrates the fish and creates the characteristic flavour of Amritsari machhi. Substituting with refined oil produces a technically similar but flavourlessly inferior result.

Bihar and Jharkhand: Mustard Fish Curry

Bihari fish curry uses a mustard paste (ground mustard seeds) cooked in mustard oil — a double mustard combination similar to Bengali shorshe preparations.

Odisha: Machha Besara

Odisha's signature fish preparation uses a paste of mustard seeds, turmeric, and green chillies, cooked in mustard oil. The dish is defined by the combination of ground mustard and mustard oil.

Assam: Masor Tenga

Assamese sour fish curry uses mustard oil for the tadka and as the cooking medium. The combination of mustard oil, tomato, and Assamese lemon (kaji nemu) creates a distinctive sour-pungent flavour profile.

How to Use Mustard Oil for Fish

Marinade

The most important application. A basic mustard oil fish marinade:

• 2 tbsp cold pressed mustard oil
• 1 tsp turmeric
• 1 tsp red chilli powder
• 1 tsp ginger-garlic paste
• Salt to taste

Marinate fish for at least 30 minutes (2 hours is better). The mustard oil penetrates the flesh and begins the flavour-building process before cooking even starts.

Frying

Heat mustard oil until it just begins to shimmer. Fry marinated fish on medium-high heat. The high smoke point of mustard oil (250°C) means it handles fish frying without breaking down.

The Bengali technique: Heat mustard oil until it smokes briefly, then reduce heat before adding fish. This brief smoking removes the raw pungency of the oil and creates a slightly nutty flavour.

Finishing

A drizzle of raw cold pressed mustard oil over a finished fish curry adds a fresh pungency that cooked mustard oil doesn't provide. This is the finishing touch in many Bengali fish preparations.

Classic Recipe: Shorshe Ilish (Hilsa in Mustard Sauce)

Ingredients (serves 4):

• 4 pieces hilsa (ilish) fish, cleaned
• 4 tbsp cold pressed mustard oil
• 3 tbsp yellow mustard seeds
• 1 tbsp black mustard seeds
• 4 green chillies
• 1 tsp turmeric
• Salt to taste
• 1 tbsp mustard oil (for finishing)

Method:

1. Soak yellow and black mustard seeds in water for 30 minutes. Blend with green chillies and a little water into a smooth paste.
2. Marinate fish with turmeric, salt, and 1 tbsp mustard oil for 30 minutes.
3. Heat 3 tbsp mustard oil in a kadai until it smokes briefly. Reduce heat.
4. Fry fish pieces for 2 minutes each side. Remove and set aside.
5. In the same oil, add mustard paste. Cook for 2 minutes on low heat.
6. Add ½ cup water. Bring to a simmer.
7. Add fried fish. Cook for 5 minutes.
8. Finish with 1 tbsp raw mustard oil drizzled over the top.
9. Serve with steamed rice.

Why No Other Oil Works

Refined oil: Produces flat, one-dimensional fish dishes. The flavour complexity that mustard oil provides is absent.

Coconut oil: Works for Kerala fish curry (a different flavour tradition) but not for North Indian or Bengali fish preparations.

Sesame oil: Too assertive in a different direction — the sesame flavour competes with fish rather than complementing it.

Olive oil: The Mediterranean flavour profile clashes with Indian spices.

Mustard oil's specific combination of pungency, high smoke point, and chemical interaction with fish compounds makes it uniquely suited for Indian fish cooking. This is why the tradition developed the way it did — not out of habit, but because it produces the best results.

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Order Cold Pressed Mustard Oil for Fish Cooking

Dune Aura delivers kachi ghani mustard oil to all major cities where fish cooking is central to the cuisine:

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• Cold Pressed Mustard Oil in Patna
• Cold Pressed Mustard Oil in Jamshedpur
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• Cold Pressed Mustard Oil — Delhi NCR Hub

Dune Aura cold pressed mustard oil is available from ₹150 for 500ml. Pure kachi ghani extraction, delivered across Delhi NCR.