Mustard Powder vs. Prepared Mustard: What’s in Each and How to Swap Them

Mustard powder is mustard seed ground to a fine, dry flour.¹ Prepared mustard is ground or cracked seed already mixed with a liquid, usually an acidic one such as vinegar, wine or verjus, plus salt and often other seasonings.² That liquid is the whole difference. In powder, mustard’s heat hasn’t been made yet: it forms only when water reaches the crushed seed.³ In prepared mustard the seed has already met its liquid, and the acid in that liquid sets how hot it stays.³ Three named guides agree on the swap: 1 teaspoon of powder for 1 tablespoon of prepared mustard.¹⁴⁵

Side by side

The two USDA records are separate analyses of different products, not the same mustard measured before and after mixing.⁹⁸

Why powder and prepared mustard taste different

Powder needs water to wake up. Crushed mustard seed holds an enzyme, myrosinase, and a glucosinolate, sinigrin. Water brings them together and the reaction forms allyl isothiocyanate, the volatile compound that gives mustard its kick.³ Until then, dry powder tastes of very little. Water that is too hot deactivates the enzyme; cold water works but slowly.³ Katzer describes English mustard, made by the Colman method, as sold dry and mixed with water shortly before use, its flavor developing within about 10 minutes.⁶

Acid sets the level. Popular Science reports that strong acidity, like vinegar’s, completely inhibits myrosinase, and that vinegar is what sets how spicy a mustard ends up.³ That is the key to mixing your own: water first, wait, then acid. Pour vinegar onto dry powder and you get a milder mustard.

Seed type matters too. Yellow mustard’s pungent compound is non-volatile and stable in acid, which Katzer gives as a reason it is usually preferred for mustard pastes.⁶¹⁰ Brown and black seed make the volatile allyl isothiocyanate instead.¹⁰ Katzer adds that the stronger pastes usually contain more acid than the milder ones made from white seed.¹⁰

The liquid and seasonings come along. Saveur describes the rules for Dijon mustard, protected by an appellation granted in 1937: only black or brown seed, mixed with wine, wine vinegar or verjus (the juice of unripe grapes), with salt and herbs such as tarragon added.² Wine vinegar, which makes a slightly more pungent mustard, is the most widely used in Dijon.² The name itself comes from Latin vinum mustum, the new wine or must that was once mixed into the crushed seed.¹¹

Can one stand in for the other?

The ratio (Attributed)

All three agree, which is rare for a substitution ratio. None says how it was arrived at. The extension charts don’t name a style of prepared mustard; McCormick gives the figure for Dijon, which it calls the best substitute for ground mustard.¹

What the swap adds or takes away (Computed)

Using USDA’s figures for yellow prepared mustard, 5 g per teaspoon,⁹ a tablespoon weighs about 15 g by our arithmetic. That tablespoon brings:

• About 12.5 g of water, roughly 2 1/2 teaspoons, from its 83.7% water content.⁹
• About 165 mg of sodium, from 1,100 mg per 100 g.⁹ The teaspoon of powder it replaces carries about 0.3 mg.⁸

These figures hold for USDA’s yellow prepared mustard only. Dijon and other styles differ, so check the label for sodium.

Powder in place of prepared mustard. Mix 1 teaspoon of powder with about 2 1/2 teaspoons of cool water, let it stand a few minutes, then add a splash of vinegar or wine if the dish wants tang. Add a pinch of salt if the recipe relied on the mustard for seasoning. The water amount comes from the arithmetic above; the rest is method.

Prepared mustard in place of powder. Use 1 tablespoon per teaspoon, and cut a little liquid and salt elsewhere in the recipe. This works in sauces, marinades, dressings, glazes and cheese sauces. It doesn’t work in a dry rub, a spice blend or a seasoned flour, where the moisture turns the mix into a paste. That is kitchen judgment.

When to use which

These are kitchen judgments, apart from the cited points:

• Mustard powder for dry rubs and spice mixes; for cheese sauces and macaroni and cheese, where it sharpens without adding vinegar; for making your own mustard to the heat you want; and anywhere you want mustard without salt or acid.
• Prepared mustard as a condiment, for sandwiches and sausages, and in vinaigrettes and mayonnaise. Katzer notes that mustard contains emulsifiers that help stabilize emulsified sauces,⁶ and prepared mustard is the easier form to whisk in.
• Yellow prepared mustard is the hot dog standard;⁷ its bright color comes from turmeric in brands that add it, not from the seed.⁶ See turmeric.

Making your own. Mustard powder is the base of homemade prepared mustard: cool water first, rest, then acid. Popular Science recommends letting homemade mustard rest in the fridge for two to three days before eating it.³ Whole-grain mustard starts from seed rather than powder; see mustard powder vs. mustard seed.

Safety

• Allergy. Mustard is one of the 14 allergens food businesses in the UK must declare,¹² in any form.
• Erucic acid (EU). EU law caps erucic acid, a fatty acid found in mustard, at 35 g/kg in mustard as a condiment.¹³ The regulation lists no separate limit for mustard powder.

What isn’t known

• The extension guides don’t say which style of prepared mustard their 1-to-3 ratio assumes, and none of the three sources says how it was derived.
• USDA’s nutrient record covers yellow prepared mustard only. Dijon, brown and whole-grain mustards were not checked.
• No source measures how hot store-bought prepared mustard is compared with powder mixed at home.

Related

• Mustard powder and mustard powder substitutes
• Mustard powder uses and mustard seed uses
• Mustard powder vs. mustard seed and yellow vs. black mustard seeds
• Yellow mustard seeds, brown mustard seeds and black mustard seeds
• Horseradish and wasabi, with the same kind of heat