Mustard oil is used in Indian cooking when a recipe calls for its bold, peppery aroma rather than a neutral cooking fat. It is especially associated with some eastern Indian cuisines, including Bengali cooking, and appears in fish dishes, vegetable preparations and pickles. Its use varies by region and household, so it is not the default oil for every Indian curry.
For fish and robust curries
In many regional recipes, mustard oil is used to cook fish or vegetables with assertive seasonings. Its distinctive flavour stands up to ingredients such as chilli, mustard seeds, turmeric and garlic. Use it when the recipe is designed around that pungency; if you substitute it for a neutral oil, the change in flavour can be noticeable.
For vegetable dishes
Mustard oil can be used to sauté or temper ingredients in dishes featuring potatoes, aubergine, greens or other vegetables. It works best when its strong aroma complements the rest of the dish. For delicate flavours, a more neutral oil may be a better fit.
For pickles and regional preparations
Some Indian pickle recipes use mustard oil as part of their characteristic flavour. Pickling methods and storage instructions differ, so follow a tested recipe rather than improvising quantities or storage times. Mustard oil may also be used in marinades or spice-led preparations when a recipe specifically calls for it.
Check the label before cooking
Mustard oil products can differ, so check that the specific product is labelled for culinary use and follow its instructions. If the label does not indicate that it is intended for food, do not use it in cooking.
In short, reach for mustard oil when you want the pungent flavour that defines a particular regional recipe, especially one featuring fish, strongly seasoned vegetables or pickles. If you want a milder result, choose an oil with a more neutral taste.