The seeds of yellow, brown and black mustard, mild until crushed with water, when an enzyme releases their nose-tingling heat. Fried whole in Indian cooking and ground for table mustard.
What it is¶
Mustard seed comes from three plants in the cabbage family, all bearing small, round seeds in narrow pods:
| Type | Species | Seed | Heat |
|---|---|---|---|
| Yellow or white | Sinapis alba | Pale straw, 2–3 mm | Mildest; heat on the tongue |
| Brown | Brassica juncea | Reddish to dark brown, smaller | Hot, sharp, rises to the nose |
| Black | Brassica nigra | Dark brown-black, smallest | Hottest and most aromatic |
True black mustard is hard to harvest mechanically, as the pods shatter, so most "black" mustard seed sold today is actually dark brown B. juncea.
Whole, dry mustard seeds have almost no heat. The pungency only appears when the seed is crushed and mixed with water: an enzyme, myrosinase, then breaks down sulphur compounds called glucosinolates into sharp, volatile isothiocyanates. See mustard-oils.
Origins and history¶
Mustard is one of the oldest spices. Seeds appear at archaeological sites across Europe and Asia, and the plant is mentioned in Sanskrit texts and in the Gospels' parable of the mustard seed. The Romans made a condiment by mixing ground seed with unfermented grape juice, mustum ardens ("burning must"), from which the word "mustard" is usually derived.
Dijon became a centre of mustard-making in the Middle Ages, and Dijon mustard is still made in the traditional way with brown seed and verjuice or white wine, though much of the seed now comes from Canada. In England, Tewkesbury was known for mustard balls, and in 1814 Jeremiah Colman began milling mustard in Norwich, founding the brand that made fine English mustard powder a household staple.
Flavour and aroma¶
Whole seed fried in oil loses its sharpness and becomes nutty, faintly bitter and savoury. Crushed and mixed with cold water, brown and black seed produce allyl isothiocyanate, the same compound that gives horseradish and wasabi their sinus-clearing heat. Yellow mustard produces a less volatile compound, so its heat stays on the tongue and does not rise to the nose. Unlike the burn of chillies, mustard heat fades quickly.
In the kitchen¶
Whole seeds¶
In India, brown or black mustard seeds are the classic opening of a tadka or tempering. Heat 1–2 tbsp oil until shimmering, add 1 tsp seeds, cover the pan and wait until they pop and crackle (about 30 seconds), then add curry leaves, chilli and asafoetida. See tempering-spices. Mustard seeds are part of panch-phoron and essential in dals, sambars, upma, coconut chutneys and lemon rice. Whole yellow seeds go into pickling spice, piccalilli and pickled onions.
Ground and prepared¶
- English mustard: yellow and brown seed ground to a fine powder, mixed with cold water and left for 10 minutes to develop its heat.
- Dijon: brown seed, hulled, with wine or verjuice; smooth and sharp.
- Wholegrain (à l'ancienne): partly crushed seed.
- American yellow mustard: mild yellow seed coloured with turmeric.
- Bengali kasundi and dishes like shorshe ilish (hilsa in mustard sauce), made with freshly ground mustard paste.
🔬 Why mustard needs cold water
Myrosinase works best in cold or lukewarm water and is damaged by heat and acid. Mix mustard powder with cold water for maximum heat; mixing with vinegar, or cooking the paste, gives a milder, more stable result. Add prepared mustard to hot sauces at the end if you want to keep its bite.
Buying and storing¶
Whole seeds keep for years because the pungency is locked away until crushed. Mustard powder keeps well for a year or more, sealed. Made-up mustard paste loses heat within hours, which is why English mustard is traditionally mixed fresh; opened jars of prepared mustard are best kept in the fridge.
Substitutes¶
For heat in dressings and sauces, a little horseradish or wasabi. For whole seeds in Indian tempering, there is no real substitute, but cumin seeds will give a different, still pleasant start. Brown and black seed are interchangeable; yellow seed is milder.
Pairs well with¶
Curry leaves, cumin, fenugreek, turmeric, asafoetida, nigella, fennel seed, tarragon, dill, honey, vinegar, pork, ham, beef, sausages, cheese, cabbage, cauliflower, potatoes, fish.
Health and safety¶
⚠️ A major allergen
Mustard is one of the 14 major allergens that must be declared on food labels in the UK and EU. Reactions can be severe. It hides in dressings, mayonnaise, sauces, spice mixes, curry powders and pickles.
Mustard oil pressed from the seed is traditionally used for cooking in Bengal and elsewhere in South Asia, but because of its erucic acid content its sale as a cooking oil is restricted in some countries, including the EU and US, where it is often labelled "for external use only". See spice-allergies.