What Are Mustard Seeds? Types, Uses & How to Cook Them
Mustard seeds are the small round seeds of the mustard plant, used across Indian, European and American cooking. In Indian cooking they're almost always black or brown, and they're fried in hot oil until they pop before anything else goes in the pan - about 30 seconds that turns them from harsh and bitter into warm and nutty.
Here's how the three types differ, how to cook with them properly, and what to use if you've run out.
What are mustard seeds?
Mustard seeds are tiny, round seeds measuring 1 to 2 millimetres across, harvested from plants in the Brassica family - the same family as cabbage, broccoli and rocket. They range from pale yellow through to dark brown-black depending on the variety.
On their own they taste sharp, pungent and slightly bitter. That pungency comes from a compound called allyl isothiocyanate, which is also what gives horseradish and wasabi their kick. Heat changes it completely, which is why the way you cook them matters more than with most spices.
Black vs brown vs yellow mustard seeds
| Type | Size & colour | Heat | Used for |
|---|---|---|---|
| Black (rai) | 1-1.5mm, dark brown to black | Strongest | Indian tempering, curries, dal, pickles |
| Brown | 1-1.5mm, light to dark brown | Medium | Same jobs as black. Also Dijon mustard. |
| Yellow / white (sarso) | 2-2.5mm, pale yellow | Mildest | American table mustard, pickling, mustard oil |
If an Indian recipe just says "mustard seeds," it means black. If it says "rai," it means black. The small jars in the regular supermarket spice aisle are usually yellow, which is a different job entirely.
Worth knowing: almost all seed sold as "black mustard" worldwide is actually brown Brassica juncea. True black mustard shatters when it ripens, so it can't be machine-harvested. It's not a quality issue - it's what every modern recipe is calibrated to.
The naming causes most of the confusion. In Hindi, black and brown seeds are rai, while yellow seeds are sarso. For the full list across Indian languages, see what mustard seeds are called in Hindi.
What do mustard seeds taste like?
Raw: sharp, pungent and bitter, closer to horseradish than to chilli. Not pleasant on their own.
Fried in oil: completely different. They pop, mellow out, and turn nutty and faintly sweet. This is the version every Indian dish is built around.
Ground into powder: the pungency comes back, which is why mustard powder works in dressings and sauces but turns bitter if you fry it.
How to use mustard seeds
The technique is called tadka (also tempering, tarka or chaunk), and it's the first step in most South Indian dishes.
Step 1: Heat 1-2 tablespoons of oil or ghee in a small pan over medium-high heat until it shimmers.
Step 2: Add 1 teaspoon of black mustard seeds. Stand back and use a lid - they jump.
Step 3: Wait 15 to 30 seconds until they splutter and pop. This is the whole point. If they don't pop, your seeds are stale.
Step 4: Add curry leaves, cumin seeds or a pinch of asafoetida straight after, then pour the lot over cooked dal or stir it through a curry base.
One teaspoon is enough for four servings. If they burn and turn black, start again - burnt mustard seeds are bitter and there's no rescuing the dish.
Do you have to fry them first?
For almost all Indian cooking, yes. Raw mustard seeds stay harsh and bitter. The exception is pickles and some dressings, where the seeds are ground raw and that sharpness is exactly what you want.
You can also dry-toast them in a pan without oil if you're grinding them for a spice blend, but for tempering, oil is what carries the flavour through the dish.
Which dishes use mustard seeds?
- Dals and lentil dishes - our yellow dal, sambar, rasam
- South Indian vegetables - cabbage thoran, beans poriyal, okra stir-fry
- Pickles (achaar) - mango, lime and chilli pickles, usually with ground seed
- Chutneys - coconut chutney, tomato chutney
- Bengali fish curries - often with mustard oil and ground mustard paste
- Outside India - pickling brines, whole grain and Dijon mustard, salad dressings
What can I use instead of mustard seeds?
The best substitute is a different colour of mustard seed - same spice, just a different heat level.
- Brown or yellow mustard seeds - closest match. Swap 1:1, or use about 1.5 tsp yellow for every 1 tsp black, since yellow is milder.
- Ground mustard powder - use 1/2 tsp per 1 tsp whole seeds. Add it during cooking, not to hot oil, or it turns bitter.
- Cumin seeds - 1:1, and the best option for tempering. Different flavour (warm and earthy rather than sharp) but used identically.
- Caraway seeds - 1:1, better suited to pickling and European baking than Indian dishes.
Full detail and more options in what to use instead of mustard seeds.
Where to buy mustard seeds in Australia
Coles and Woolworths both stock 250g bags of black mustard seed in the international aisle, though availability varies by store. ALDI doesn't carry them. Indian grocers are reliable but usually sell in 500g or larger.
Our black mustard seeds are sourced from India and packed in Brisbane, shipped Australia-wide.
Mustard seed nutrition
Per 1 teaspoon (about 3g):
| Nutrient | Per 3g | Per 100g |
|---|---|---|
| Energy | 64 kJ (15 Cal) | 2126 kJ (508 Cal) |
| Protein | 0.8 g | 26.1 g |
| Fat, total | 1.1 g | 36.2 g |
| Carbohydrate | 0.8 g | 28.1 g |
| Dietary fibre | 0.4 g | 12.2 g |
| Sodium | <1 mg | 13 mg |
Values are indicative, based on published composition data for whole mustard seed.
Frequently asked questions
Are mustard seeds spicy?
Pungent rather than chilli-hot - closer to horseradish or wasabi. Frying removes most of that sharpness and leaves a nutty sweetness.
Are mustard seeds and mustard powder the same?
No. Mustard powder is ground yellow seed. It won't temper and it turns bitter in hot oil, so the two aren't interchangeable in Indian cooking.
What are mustard seeds called in Hindi?
Black and brown seeds are rai (राई), yellow are sarso (सरसों). Kali rai means black mustard specifically.
How much should I use?
One teaspoon per four servings is standard for tempering. They're potent, so more isn't better.
How long do mustard seeds last?
Around two years sealed, stored away from heat and light. If they don't pop in hot oil, replace them.
Can I grind mustard seeds at home?
Yes. Toast them dry first, then grind in a spice grinder or mortar and pestle. Grind small amounts as needed. Ground mustard loses its punch within months.
About the author
We're a small family business based in Brisbane, bringing authentic Indian spices to Australian kitchens. We work directly with suppliers in India and pack everything here.
