Brown Mustard Seeds: The Seed Behind Dijon, Mustard Oil and Mustard Greens

Bought mustard seed in the West lately? It was probably brown. Brown mustard has almost completely replaced true black mustard as a seed crop, and it brings the heat in a lot of French-style mustards and the pop in South Indian tempering. The small, round seeds come from Brassica juncea, the plant that also gives you mustard greens and, across much of South Asia, cooking oil. To keep that heat, mix ground seed with water that isn’t too hot, and add vinegar to lock it in.

At a glance

What brown mustard is

Three plants supply the world’s mustard seed: white or yellow mustard (Sinapis alba), black mustard (Brassica nigra, which Kew now files as Mutarda nigra) and brown mustard (B. juncea). Kew treats brown mustard as a hybrid of Brassica rapa and black mustard, native to the Caucasus.¹ Britannica puts its home in the Himalayas instead.² Gernot Katzer groups several kinds under the species: Sarepta or Romanian brown mustard from Eastern Europe, and what he calls Indian brown mustard, which he describes as a fertile hybrid.³

Britannica describes the seeds as dark yellow and about 2.5 mm across.² Katzer says they’re bigger than black mustard seeds, up to 2 mm, and lighter in color.³

Why brown replaced black

Brown mustard can be harvested by machine and black mustard can’t, and Britannica says brown has almost entirely replaced black for seed.² Katzer calls brown mustard the dominant quality on the European market and says Indian brown mustard is probably what you’re buying in the West.³ For the older species, see black mustard seeds.

Flavor and the compounds behind it

Whole, dry mustard seeds don’t smell like anything. The heat only shows up once the seed is crushed and wet. Mustard seeds hold a glucosinolate, sinigrin, and an enzyme, myrosinase. Add water and the two meet, and the enzyme releases allyl isothiocyanate (AITC), the volatile compound behind mustard’s sinus-clearing bite. In Romanian brown mustard, Katzer reports a related compound, crotonyl isothiocyanate, alongside AITC.³

Here’s how the sources rank strength:

So brown isn’t the hottest mustard seed, despite what you’ll sometimes read, but it’s well ahead of yellow. Fry or dry-toast mustard seeds and they lose their bite and turn nutty and smoky, because heat destroys the isothiocyanates that have formed.³ There’s a slight bitterness in the background too.

Keeping the heat

The enzyme behind the heat is touchy about temperature. In a lab comparison, inactivation of brown mustard seed myrosinase climbed as temperature rose from 30 to 80 °C.⁷ Popular Science advises mixing ground mustard with water that isn’t too hot, since very hot water shuts the enzyme down entirely. It also notes that vinegar, being strongly acidic, stops the reaction and locks in the heat level.⁶ For the full method, see mustard powder and mustard powder vs. mustard seed.

How brown mustard seeds are used

Prepared mustard

Brown mustard seeds are characteristic of many French-type paste mustards. Writing in Saveur, William Sertl reports that mustard sold as Dijon may be made only with black or brown mustard seed, mixed with wine, wine vinegar or verjus (the juice of unripe grapes), under rules dating to 1937. The rules cover the seeds and liquids, not where the seed is grown, and most of the seed in Dijon mustards today comes from Canada.⁸ The Saskatchewan government says Europe is the main market for brown mustard and that the province’s growers are the world’s largest mustard exporters.⁴ Katzer adds that white mustard is usually preferred for milder pastes.

Brown mustard often gets named as the seed in English, Düsseldorf and American “spicy brown” mustards. We couldn’t find a source documenting the seed blend in any of those styles, so we’re not stating it.

Indian cooking

Katzer describes frying whole mustard seeds in hot fat as a typical South Indian technique, and lists mustard among the five seeds of the Bengali mix panch phoron. He covers these uses under black mustard, while noting that brown is now the type mostly traded. In this cooking, whole seeds always get fried in fat or dry-toasted first.³ See panch phoran, curry leaves, cumin and coriander, the seed’s usual companions.

Oil and greens

B. juncea is an important oil crop in northern India, Pakistan, China, southern Russia and Kazakhstan. Saskatchewan’s oriental type goes mostly to Asia, where it’s used as a cooking oil and a condiment. Katzer puts the heart of mustard oil cooking in West Bengal and Bangladesh.³

The leaves and swollen leaf stems are eaten as greens, and they’re especially important vegetables in much of Asia and Africa. In China, a variety with fleshy, swollen stems (B. juncea var. tsatsai) is salted, fermented with chile paste and sold as zha cai, known in English as Sichuan vegetable or Chinese pickled mustard.³

For more ideas, see mustard seed uses.

Buying and quality

We didn’t find a grading standard for retail brown mustard seed. Look for whole, evenly sized, hard, unbroken seeds with no dust or debris. Whole seeds have no smell, so sniffing the jar won’t tell you much. Crack a few and add a drop of water first.

Storage

We found no published shelf-life figure for whole or ground brown mustard seed from a regulator or standards body. Keep whole seed sealed, cool and dry, and grind it as you need it.

Safety

• Allergen. Mustard is one of the 14 allergens that UK food businesses must declare.⁹ It isn’t one of the nine major food allergens under US law.¹⁰
• Erucic acid. The EU sets maximum levels of erucic acid for mustard products: 35 g/kg for mustard as a condiment, and 50 g/kg for mustard oil, with an exemption for locally produced and consumed oil.¹¹

Health claims

Brown mustard seed often gets promoted for minerals, vitamins and disease protection. We found no regulator summary or systematic review on brown mustard seed as a food that backs those claims up. We’re not claiming it treats or prevents anything.

Substitutes and comparisons

Black mustard seed is the closest swap, a little sharper. Yellow seed is milder. Ratio (Method): Start one for one and adjust to taste. See black mustard seed substitutes, yellow vs. black mustard seeds, yellow mustard seeds, mustard powder substitutes, mustard powder uses and mustard powder vs. prepared mustard.