Abba (Brassica juncea): Mustard Seed, the Tempering Spice With Hidden Chemistry

Abba (Brassica juncea) is the tiny brown seed that crackles in hot coconut oil at the start of almost every Sri Lankan curry, releasing the sharp, nutty aroma that means dinner is on the way. It is also the base of the fiery mustard paste in Sinhala pickles and, in village medicine, the heat behind poultices for stiff joints and congested chests. Beneath the familiar flavour lies a family of sulphur compounds, the glucosinolates, that nutrition scientists have been studying with mounting interest.

Botanical and Cultural Background

Brown mustard is an annual of the cabbage family, grown across northern India and imported into Sri Lanka as seed. When the seeds are crushed and moistened, an enzyme converts their glucosinolates into pungent isothiocyanates — the same chemistry that makes wasabi and horseradish hot, and the reason mustard seeds are mild until ground. The seed oil is a cooking and massage oil in South Asia, and the young leaves are a green vegetable. Ayurveda classes mustard (sarshapa) as strongly heating.

Traditional Uses in Sri Lankan Medicine

• Digestion and appetite — tempered seeds in curries as a carminative; mustard pickle to stimulate appetite.
• Joint pain — mustard poultice or warmed mustard oil massage for stiff, aching joints.
• Chest congestion — a mustard plaster on the chest for coughs and colds in older practice.
• Skin — ground seed paste for itching and ringworm.

What the Research Shows

A 2025 review in Frontiers in Nutrition surveyed mustard's phytochemistry — glucosinolates, phenolic acids, flavonoids and the fatty-acid profile of the oil — and documented antioxidant, anti-inflammatory, antimicrobial and cholesterol-related effects in laboratory and animal work. A 2023 systematic review in Nutrients examined glucosinolates and their isothiocyanate derivatives across the cabbage family and found consistent evidence of metabolic benefits, including antioxidant defence and anti-inflammatory signalling, mostly from animal and cell studies with a smaller number of human trials on cruciferous vegetables generally. The counter-irritant effect of mustard on skin — the basis of the poultice — is real and well explained by isothiocyanate activation of pain and heat receptors. Trials of mustard seed itself in people are lacking.

Evidence updated September 2026.

How Abba Is Prepared

In cooking, temper whole seeds in hot oil until they pop, then add the other ingredients. For mustard paste, grind seeds with a little vinegar or lime juice and salt; the heat develops over ten minutes. For a joint poultice, mix ground seed with warm water into a paste, spread on a cloth (not directly on skin) and apply for no more than fifteen minutes. Warmed mustard oil is massaged into joints in the same way.

Safety and Precautions

Culinary use is safe. Mustard poultices and plasters can blister the skin if left too long or applied directly — always use a cloth barrier and stop at the first sign of burning; never use on children or broken skin. Mustard seed oil sold for massage is not always food-grade and may contain erucic acid in amounts unsuitable for cooking. Mustard is a common allergen; people with cruciferous allergies should avoid it.