A compliment for a condiment: Swetha Sivakumar on mustard

The “mustard oil bomb” is one of the most-studied defence systems in the plant kingdom. In its war for survival against moths, caterpillars and other herbivores, this plant literally built itself an arsenal. Tucked within a compartment in each seed is an enzyme called myrosinase. When an insect or animal gets at the seed, this compartment breaks open. The enzyme is exposed to air and saliva, and gets to work. It reacts with the pungent glucosinolate in the seed to produce pungent, volatile isothiocyanates that attack the eater’s sinuses, eyes and nose with their vapours.

The nibbler stumbles away from the plant, surprised and hurt. Unless it’s a human. We love the sensory invasion that comes from the vapours of ingredients such as mustard and wasabi. Aside from tasting great, the glucosinolate-myrosinase compounds in mustard have proven to have anti-carcinogenic, anti-inflammatory properties. Given these benefits, we willingly plant it. Thus, in a sense, the mustard plant wins after all.

Although, we have also found ways to disarm it. Manipulating the myrosinase in the mustard seed produces a Jekyll and Hyde effect. Expose the seed or its oil to high heat (80 degrees Celsius or more), and the enzyme is denatured. This is why mustard seeds popped in a tadka taste nutty, with no trace of pungency. Mustard oil, when heated to its smoking point, loses that sharp pungency too.

Room-temperature mustard oil, however, still smells strong, as though it somehow retained all the anger of the crushed seeds. Some cuisines (Bengali, Kashmiri) have found delicious ways to embrace this oil’s strong fragrance and flavour. For many, it remains an acquired taste.

There are three main types of mustard seeds available today: black, brown and yellow. Black mustard is native to India and contains the most glucosinolate. Brown and yellow mustard are progressively less pungent as they carry less and less of it. The West prefers yellow mustard for this reason. American mustard is made exclusively from yellow-mustard seeds, with turmeric added for a brighter colour, and acid added to tame the enzyme (just as heat does in a tadka).

To see this chemistry play out, take a spoon of powdered mustard and dissolve half in water and half in vinegar. The mustard water will carry a lot more pungency, vapours and heat than the mustard vinegar, because of the action of the acid in the latter.

Most mustard condiments in the West use some form of acid to temper the pungency. The Indian mustard condiment kasundi does not. It is traditionally made by fermenting raw mango and mustard in water, then topping it with oil. That puts kasundi at one end of the pungency spectrum, American mustard at the other.

Where does Dijon mustard fall? The traditional recipe for this French condiment involves grinding mustard with verjus (the juice of unripe grapes). Verjus is less acidic than vinegar and produces a sharper but more-well-rounded taste. Commercial Dijon mustard usually substitutes the verjus with white wine, to give the product a longer shelf life. Either way, that puts Dijon mustard somewhere in the middle of our scale.

Now, there’s one more secret quality to the mustard seed: Because of the way it is built, it helps emulsify liquids. A vinaigrette made with just oil and vinegar will separate in a few minutes, but add just a small amount of mustard (especially wholegrain) and the dressing will retain its consistency for hours. This is because mustard bran is rich in gelatinous mucilage, which binds the oil and vinegar together.

Well, that’s mustard in a nutshell. For such a small seed, it certainly gets a lot done.

(To reach Swetha Sivakumar with questions or feedback, email [email protected])