Columella's Roman mustard, the seed pounded into unfermented grape must that gave the condiment its name
Origin: Rome, Roman Empire
From the journey of Mustard.
This is where the word comes from. Romans ground mustard seed into mustum, the unfermented juice of freshly pressed grapes, and called the result mustum ardens, burning must. Old French contracted it to mostarde and English to mustard, which means that every jar in Europe is named after grape juice rather than after the plant. Columella set down the method in the twelfth book of the De Re Rustica in the first century, and read closely it is a technically sound document rather than an antiquarian curiosity. He specifies that the seed be sieved clean of grit, washed in cold water, left to soak, drained, pounded in a mortar, and worked with must into a smooth paste, with a little vinegar added at the end and the whole thing passed through a sieve. The detail that matters is the cold water, and Columella cannot have known why he was right. Mustard seed contains no heat at all until it is crushed and wetted, at which point an enzyme in the seed converts a stored compound into the pungent one. That enzyme is destroyed by heat. A Roman writer specifying cold water and a soaking time was describing, without any means of explaining it, exactly the conditions the reaction requires, and every modern instruction to mix English mustard powder with cold water and wait ten minutes is the same rule restated. What it tastes like is not what a modern palate expects. Grape must is sweet and slightly tannic rather than sour, so the result is rounder and fruitier than a vinegar mustard, closer in spirit to an Italian mostarda or a Bavarian sweet mustard than to Dijon. Served with cold roast meats and boiled vegetables, it is a genuinely good condiment and not merely an interesting one.
The mustard is at its fiercest the day it is made and settles into something rounder and more balanced over a week. It keeps for two months refrigerated and slowly loses pungency thereafter. Grape must is available in autumn from vineyards and from Italian grocers as mosto; failing that, good unfiltered white grape juice reduced as described is a fair substitute. Saba or vin cotto, the reduced must sold by Italian delicatessens, can be used directly and diluted with water. Columella's own version has no honey and no coriander, and both are noted here as optional for that reason. He does mention adding a small quantity of pine nuts or almonds to some versions, which thickens the paste and is worth trying. Serve with cold roast pork or beef, with boiled ham, with hard cheese, and with plain boiled vegetables, which is roughly what Rome ate it with.
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