Kali Sarson / Black Mustard (Brassica nigra) is a round hard seed, varying in colour from dark brown to black. It is smaller and much more pungent than the white variety. It is used to season foods, mostly added as a tempering or as a powder.

The mustard seeds are known to be an excellent source of calcium, magnesium, selenium, potassium and phosphorus. They also contain vitamins like vitamin A, vitamin K, vitamin C and folate. The isothiocyanates and other phenol compounds in mustard seeds are known to prevent cancer and also exhibit anti-inflammatory and anti-bacterial properties. Mustard seeds are usually consumed in small quantities, often as a tempering. Consuming large amounts of these seeds might cause abdominal discomfort.