Three species in substantial use, and they are not interchangeable: Sinapis alba, white or yellow mustard, mild; Brassica juncea, brown or Indian mustard, hot, and the commercial workhorse; and Brassica nigra, black mustard, the fiercest of the three and now largely confined to South Indian cooking because it shatters before a machine can harvest it
Origin: Three homelands, because these are three plants. <em>Brassica nigra</em> and <em>Sinapis alba</em> are both Mediterranean and Near Eastern natives, the black centred on the eastern end of that arc and the white spread across the basin more broadly. <em>Brassica juncea</em> is younger and hybrid, and arose where the ranges of <em>B. rapa</em> and <em>B. nigra</em> overlapped somewhere between the Iranian plateau and the Central Asian foothills, with India and China as its great secondary centres.
Mustard is three crops wearing one name, and the differences between them are the whole practical story of the ingredient.
Sinapis alba gives a large pale seed and a mild heat. Brassica juncea gives a smaller reddish-brown seed and a fierce one. Brassica nigra gives the smallest and hottest seed of all, and has been quietly abandoned by the world's farmers because its pods shatter the moment they ripen and scatter the crop on the ground. That was tolerable for hand-harvesting and impossible for a combine, so from the middle of the twentieth century commercial growers replaced it almost everywhere with B. juncea, which holds its pods. Black mustard survives in South India, where it is still grown and where the tempering pan wants precisely its violence.
The relationship between the three is one of the tidiest pieces of plant genetics in the kitchen. What botanists call the Triangle of U sets out how six Brassica species relate: three are simple, and three are hybrids formed when the first three doubled up. B. nigra crossed with B. rapa, the turnip, produced B. juncea; B. nigra crossed with B. oleracea, the cabbage, produced B. carinata, the Ethiopian mustard. Brown mustard is therefore, quite literally, black mustard and turnip in a single plant.
What is grown from these three is not only seed. B. juncea is a leaf vegetable across China, India, Japan, and the American South, and one Chinese variety, tumida, has been selected for a swollen knobbled stem that is pickled into zha cai. In the Punjab the leaf is the point and the seed is a by-product; in Bengal the oil is the point; in Dijon the seed is everything and the plant itself is never seen.
Canada now grows that seed. Saskatchewan supplies somewhere between two thirds and four fifths of the world's traded mustard seed, including most of what Dijon grinds, and when the prairie harvest failed in the drought of 2021 France ran out of mustard the following year and the empty shelves made the national news. It is a fair illustration of how far a condiment can sit from the field that feeds it.
Mustard did not need to travel far, because two of its three species were already native across the Mediterranean and the third arose on the far side of Persia. What travelled was the idea of grinding the seed and wetting it, and the traditions that grew out of that idea diverged so completely that a Bengali cook and a Burgundian one would not recognise each other's mustard as the same thing.
The western line runs through Rome. Greeks and Romans both used sinapi, but it was the Romans who ground the seed into unfermented grape must and produced mustum ardens, burning must, from which the English word descends; Columella wrote down a recipe for it in the first century. The technique passed into Gaul, and by the thirteenth century Dijon was a mustard town. By the fourteenth it was regulated, and in the eighteenth Jean Naigeon replaced the vinegar with verjuice, the sour juice of unripe grapes, and gave Dijon mustard the character it still has. From France the table condiment spread into Germany and into England, where Mrs Clements of Durham worked out how to mill mustard flour as though it were wheat, and eventually across the Atlantic.
A second and quite separate line runs east from the Iranian plateau. Brassica juncea reached the Indus by around 2300 BCE and became there something the western tradition never made of it: an oil. Bengal presses it raw and cooks in almost nothing else; the Punjab grows the leaf and eats it as the dish of winter; South India throws the black seed into hot fat and waits for it to burst. Further east the same species reached China, which pickled its leaves and its stems, and Japan, which made karashi, a mustard mixed with water and nothing whatever else.
The two lines met again in unlikely places. Moravian settlers on the Volga at Sarepta began pressing B. juncea for oil in 1801 and produced a table mustard fiercer than anything in Europe. American manufacturers took the mildest of the three species, coloured it with turmeric, and sold it on a hot dog. And in Senegal, French colonial trade left Dijon mustard behind in the Casamance, where it became the base of poulet yassa, a dish now eaten across West Africa and a good deal more famous than most of what Dijon makes with it.
Mustard is the most chemically interesting thing on the condiment shelf, and nearly everything cooks get wrong about it follows from not knowing one fact.
A mustard seed contains no heat at all. It holds a glucosinolate, sinigrin in the brown and black species and sinalbin in the white, and it separately holds an enzyme, myrosinase, and the two are kept in different cells. Nothing happens until the seed is both crushed and wetted, at which point the enzyme meets the glucosinolate and converts it into an isothiocyanate. That single fact governs the entire technique. Dry mustard powder is inert. It must be mixed with cold water, because heat destroys the enzyme before it can act. It must then be left alone for about ten minutes, because the reaction is not instant. Vinegar or any other acid added at the start halts the reaction early and locks in a harsh, bitter mustard, which is why the acid goes in after the wait and never before. And a made mustard left uncovered loses its pungency within the hour, because the compound is volatile and simply leaves.
Which species is used decides where the heat is felt. Sinapis alba produces a non-volatile compound that sits on the tongue and stays there, which is the broad warm heat of an American yellow mustard. Brassica juncea and B. nigra produce allyl isothiocyanate, which is volatile, travels up the back of the nose, and is responsible for the sensation of English mustard, wasabi, and horseradish clearing the sinuses of anybody who has taken too much at once. Most made mustards blend the two deliberately.
Mustard's other job is invisible, and it is the reason a jar sits in every professional kitchen. The seed coat carries mucilage, a powerful emulsifier, so a spoonful holds oil and vinegar together in a vinaigrette and stabilises a mayonnaise that would otherwise break. It is in most dressings for its physics rather than its flavour.
By volume the plant matters far more as an oilseed and a vegetable than as a condiment. India presses B. juncea into the pungent cold-pressed kachi ghani oil that is the defining fat of Bengali and much North Indian cooking; China and India between them eat enormous quantities of the leaf; and Canada grows the seed that most of Europe's jars are filled from. The little pot on the table is the smallest part of the crop.
Historical Journey of Mustard
South-Eastern Anatolia & the Eastern Mediterranean — c. 4000 BCE
Black mustard, Brassica nigra, is native to the eastern end of the Mediterranean arc and out across Anatolia into the Near East, and it is the mustard of the classical world. When a Greek writes sínapi or a Roman sinapis, this is very largely the plant meant, and it is the one the gospels have in mind as the least of seeds.
It is the hottest of the three cultivated mustards and the most awkward to grow. The pods shatter as soon as they ripen and throw the seed on the ground, which suited a landscape of hand-harvesting and small plots and became fatal once agriculture mechanised. From about the middle of the twentieth century the world's growers gave it up almost entirely in favour of brown mustard, which holds its pods and can be cut by a combine.
This point carries no dish, and deliberately so. Black mustard's living kitchen is not here but four thousand miles east, in South India, where it is still grown and where the tempering pan is built around exactly the qualities that made it commercially impossible. What the eastern Mediterranean contributed was the plant, the Greek name, and the Roman technique that everything west of here descends from.
The Northern Mediterranean & the Balkan Rim — c. 3500 BCE
White mustard, Sinapis alba, is the second of the three and the mild one. It is native across the Mediterranean basin, spread more evenly through it than black mustard, and it produces a seed roughly twice the size and a fraction of the heat.
The difference is not a matter of degree but of chemistry. White mustard carries sinalbin rather than sinigrin, and the compound this yields when the seed is crushed and wetted is not volatile. It therefore sits on the tongue and stays there, giving a broad, warm, forward heat instead of the sharp rush up the back of the nose that black and brown mustard produce. That is why an American yellow mustard can be eaten by the spoonful and an English one cannot, and it is why almost every commercial mustard in the world blends the two species deliberately, using the white for body and the brown for attack.
White mustard is also the one that gets grown for other reasons entirely: as a green manure ploughed back into the soil, as a fodder crop, and as the sprouting half of mustard and cress on a windowsill. Like the black, it carries no dish of its own here. It is an ingredient of other people's mustards rather than the subject of a cuisine, and its own points on this map are Dijon, Norwich, and the Carolina midlands.
Khorasan, the Iranian Plateau & the Central Asian Foothills — c. 3000 BCE
The third mustard was not found but made, and it made itself. Brassica juncea is an amphidiploid, a natural hybrid formed where black mustard and the turnip, B. rapa, grew alongside one another and crossed, doubling their chromosomes into a new and fertile species. That overlap sits between the Iranian plateau and the foothills of Central Asia, which is where this point stands.
It turned out to be the most useful of the three by a wide margin. It carries the fierce sinigrin chemistry of black mustard but holds its pods like a sensible crop, so it can be harvested by machine; its leaves are large and edible where black mustard's are not; and its seed presses readily into oil. Nearly all of the world's commercial mustard seed is now this species, including the seed behind most Dijon, and so is nearly all of the world's mustard oil and mustard greens.
From here it went in two directions and became two entirely separate cuisines. South and east into the Indus and the Gangetic plain, where it became an oil and a winter vegetable and never became a condiment at all; and east across the steppe into China, which selected it for leaf and stem and pickled both. India and China are its great secondary centres of diversity, and between them they hold far more variation in the plant than its actual homeland does.
The Punjab & the Indus Plain — c. 2300 BCE
Mustard seed turns up in the Indus Valley by about 2300 BCE, at Chanhu-daro and elsewhere, which makes it one of the earliest crops recorded on the subcontinent, and Sanskrit has a word for it, sarṣapa, that descends unbroken into modern Hindi sarson.
What the Punjab does with the plant is the thing the western tradition never thought to do: it eats the leaf. Sarson ka saag is the winter dish of the region, mustard greens cooked down for hours with spinach and bathua until they collapse, thickened with maize flour, and finished with an aggressive quantity of ghee or white butter. It is eaten with makki di roti, the maize flatbread, and the pairing is so fixed that the two are effectively one dish. It belongs to the cold months, when the mustard fields around Amritsar and Ludhiana turn the whole plain yellow and the crop is at its most tender.
The seed matters here too, and mostly as oil. Mustard oil is the standard cooking fat of the north, pressed cold in the kachi ghani style so that it keeps its pungency, and used for pickling, for frying, and for the massage of infants. Punjabi cooking runs on it in the way that southern Italian cooking runs on olive oil, and a great many North Indian dishes taste distinctly wrong when it is replaced.
The Malabar Coast, Tamil Country & the Deccan — c. 300 BCE
South India is where black mustard survived, and it survived because of a technique rather than a dish.
Tadka, called thalippu or thaalikka in the south, is the operation that opens or closes almost every savoury dish in the region. Fat is heated until it shimmers, whole spices go in, and the cook waits for the mustard seeds to burst. The popping is not incidental noise but the signal: heat drives the seed to split and its raw sharpness turns nutty and rounded, and until that happens the tempering is not ready. Curry leaves, dried chilli, urad dal, and asafoetida follow into the same fat, and the whole thing is poured over the dish at the end or built under it at the start.
Black mustard, kadugu, is what the south uses for this and what it still grows, because the small hard seed pops fastest and hottest. That is precisely the property that made it commercially hopeless elsewhere, so the species that the rest of the world abandoned in the twentieth century remains ordinary here.
The consequence is that mustard is present in South Indian cooking far more often than any list of ingredients would suggest, and almost never as a flavour anybody names. It is in the curd rice eaten at the end of a meal, in lemon rice, in every rasam and kuzhambu and poriyal, and in the sweet-sour ginger relish inji puli served at the Onam feast. It is a technique before it is a taste.
Rome & the Roman Empire — c. 50 CE
Rome did not discover mustard, but it invented the word and the thing the word describes, and everything west of here descends from what happened in a Roman kitchen.
The Greeks had used sínapi as a medicine and a seasoning. What the Romans did was grind the seed and mix it into mustum, the unfermented juice of pressed grapes, producing a paste they called mustum ardens: burning must. That is the ancestor of every jar of mustard in Europe, and the name survived the recipe. Old French took it as mostarde and English as mustard, so the word describes the grape juice rather than the plant, which is why the Italian mostarda of Cremona still carries it whilst containing almost no mustard at all.
Columella set down an actual recipe in the first century, in the twelfth book of the De Re Rustica: the seed sieved and cleaned, washed in cold water, pounded in a mortar, and worked with must and a little vinegar into a paste for the table. Read closely, it is a technically sound document. He specifies cold water, and cold water is exactly what the chemistry requires, because heat destroys the enzyme that generates the pungency in the first place. Pliny discusses the plant at length and complains, as he complains about most things, that it grows wherever it likes and cannot be got rid of.
Italy kept the habit and then largely lost it as a table condiment, retaining mustard chiefly as an essence in the candied-fruit mostarde of the north. The line that mattered went west into Gaul.
Bengal & the Gangetic Delta — c. 500 CE
No cuisine on earth is built on mustard as completely as Bengal's, and Bengal uses it in three forms at once, none of which resembles a European condiment.
The first is the oil. Kachi ghani mustard oil, cold-pressed and deliberately pungent, is the fat that Bengali cooking is made in, and it is not interchangeable with anything. It is heated to smoking to take the raw edge off it for most cooking, and it is used entirely raw, by the spoonful, over rice and over mashed vegetables, where the sinus-clearing bite is the whole point.
The second is the paste. Shorshe bata is mustard seed ground with green chilli and a little water into a wet paste, and it becomes the sauce itself rather than a seasoning within one. Shorshe ilish, hilsa steamed in mustard paste, is the dish Bengal is judged by, and it demands a specific technique, because mustard ground carelessly turns bitter. The seed must be soaked, ground with salt and chilli rather than alone, and never over-processed.
The third is kasundi, a fermented mustard condiment made in the sun with mustard seed, mango, and spices, traditionally prepared by women under ritual conditions and now sold in bottles across the country. It is the closest thing in India to a European table mustard and predates any contact with one.
Around these three sit the seed itself in panch phoron, the five-spice mixture of the eastern plains, and the leaf eaten as a winter green. The deltas of the Ganges and the Brahmaputra grow the crop in enormous quantity, and Bengal, West and East alike, eats most of it.
Sichuan, Chongqing & the Yangtze — c. 800 CE
China took Brassica juncea and selected it for parts of the plant that nobody else was interested in, then pickled all of them.
The most remarkable is the stem. The variety tumida has been bred until the base of the stem swells into a knobbled green fist the size of a fist, and that swollen stem, salted, pressed, rubbed with chilli and Sichuan pepper and fermented, becomes zha cai. It comes from Fuling on the Yangtze, where it has been made commercially since the end of the nineteenth century, and it is one of the most widely eaten preserved vegetables in the world: crunchy, salty, sour, and faintly numbing, shredded into noodles and congee and stir-fries or simply eaten with rice porridge at breakfast.
The leaves go the same way. Xue cai is salted snow vegetable, mei gan cai is the dried and preserved mustard green of Hakka cooking, suan cai is the sour fermented one that goes into Taiwanese beef noodle soup, and ya cai is the Yibin version that is essential to a proper dan dan mian. Each is a different cultivar preserved by a different method, and Chinese cooks treat them as entirely separate ingredients rather than variations on a theme.
What China did not make from mustard, until very recently, is a table condiment in the European sense. The plant here is a vegetable, and the preserving jar rather than the mustard pot is where it ends up.
Bharatpur & Marwar, Rajasthan — c. 1200 CE
Rajasthan grows more mustard than any other Indian state, somewhere around two fifths of the national crop, and it does so on land that will support very little else.
Mustard is a rabi crop, sown after the monsoon and grown through the cool dry months on the moisture left in the soil rather than on rain or irrigation. That suits a semi-arid state exactly, and the belt running through Bharatpur, Alwar, Sri Ganganagar, and Tonk turns solid yellow every January. The seed goes to the oil mills, and cold-pressed kachi ghani oil comes back out as the cooking fat of the entire region.
Further west, in the desert proper, that fat has to do more work than anywhere else in India. Marwar, the country around Jodhpur and Jaisalmer, has almost no fresh vegetables for much of the year, and the Marwari kitchen was built instead on things that keep: pulses, buttermilk, dried desert fruits, red chilli, and clarified butter or mustard oil. Nothing in it is a garnish. Ker sangri, made from dried caper berries and khejri pods that have been soaked overnight, is cooked in mustard oil taken to smoking point, which is a step the dish genuinely depends on; and ker ka achar is a pickle held together by three hundred millilitres of the stuff standing above the fruit as a seal.
The two uses sit at opposite ends of the same crop. In the east of the state mustard is an oilseed grown by the million tonne for a national market; in the west it is the one fat available to a cuisine that had to be built out of whatever survived a desert year.
Dijon & Burgundy — c. 1300 CE
Dijon is the most famous mustard in the world and almost nothing about that reputation is protected, which is the first thing to understand about it.
The town was making mustard commercially by the thirteenth century and taking it seriously by the fourteenth: a Burgundian ducal banquet is recorded getting through hundreds of litres of the stuff, and a royal ordinance of 1390 regulated what could be put in it. In 1634 the vinegar-makers of Dijon were granted the exclusive right to produce it. The decisive change came later, when Jean Naigeon replaced the vinegar with verjus, the sour juice of unripe grapes, which is gentler and rounder and let the mustard's own sharpness come forward instead of being buried. That is the character the name still means. Maille was founded in 1747 and Grey-Poupon in 1866, and between them they made Dijon a word that travels.
What the word does not mean is a place of origin. Moutarde de Dijon is a style and not a designation, it may be made anywhere, and most of it is; the seed is overwhelmingly Canadian, and only the separate Moutarde de Bourgogne protects both Burgundian seed and Burgundian wine. The dependency became national news in 2022, when a failed prairie harvest emptied French shelves of mustard for months.
France uses it structurally rather than as a relish. A spoonful in a vinaigrette is there for its mucilage, which holds oil and vinegar in suspension, as much as for its taste; it thickens and sharpens the pan sauces of the bistro repertoire; it coats a rabbit before roasting; and it underpins rémoulade, ravigote, and gribiche. It is less a condiment here than an ingredient.
Cremona, Mantua & the Lombard Plain — c. 1400 CE
Northern Italy kept the Roman word and used it for something almost nobody outside Italy expects.
Mostarda is not mustard. It is whole or large pieces of fruit, candied slowly in sugar syrup until they are translucent and still hold their shape, and then sharpened with mustard essence until the syrup burns. Cremona makes the famous version, a glittering jar of whole cherries, figs, pears, apricots, and clementines that looks like a sweetshop and hits like horseradish. Mantua makes a plainer one from a single fruit, usually quince or apple, chopped rather than whole. Vicenza, Voghera, and half a dozen other towns each have their own.
It is medieval, and its logic is medieval: fruit preserved in sugar is a luxury, mustard is a preservative and a stimulant of appetite, and the combination of sweet and violent was exactly to the taste of a late-medieval northern Italian table. It survived where the plain condiment did not, which is why Italy has almost no tradition of mustard in a pot and a strong one of mustard in a fruit jar.
What it is eaten with has not changed either. Mostarda is the compulsory accompaniment to bollito misto, the great platter of boiled meats that is the winter centrepiece of Lombardy, Emilia, and Piedmont, where its sweetness and its heat cut through several hours of simmered beef and tongue and cotechino. It is also served with aged cheese, and the Mantuan version is worked into the filling of tortelli di zucca, where it does the same job against sweet pumpkin.
Tewkesbury, Durham & Norwich — c. 1600 CE
England took mustard in a direction France did not, and made it a great deal hotter.
The medieval English form was a ball. Mustard flour was mixed with horseradish and a little vinegar, dried into hard balls, and sold to be crumbled into liquid at the table; Tewkesbury made the best of them, and they were famous enough that Shakespeare uses them as an insult, Falstaff observing of Poins that his wit is as thick as Tewkesbury mustard. The next step was milling. A Mrs Clements of Durham is credited, around 1720, with working out how to grind and sift mustard seed into a fine flour in the way that wheat was milled, separating out the husk and giving a smooth powder that kept.
The name that stuck came a century later. Jeremiah Colman took over a mill outside Norwich in 1814, blended Brassica juncea for heat with Sinapis alba for body, sold the result as a bright yellow powder in a tin, and built one of the most recognisable brands in Britain. English mustard is still sold as a powder as much as a paste, and it is still made the correct way, which is to say mixed with cold water and left for ten minutes and no vinegar at all.
Where it goes is fixed by custom. Roast beef, ham, sausages, pork pies, and cheese; into a Welsh rarebit, where its sharpness is what stops a pool of melted cheese from being merely rich; and into the dressings and sauces of the Victorian kitchen. It is used in far smaller quantities than French mustard, and it needs to be.
Kumamoto, Kyushu & Edo Japan — c. 1650 CE
Japanese mustard is the purest version of the thing anywhere, because it contains nothing but mustard and water.
Karashi is made from Brassica juncea ground to a powder and mixed with tepid water into a stiff paste, then left covered for a few minutes and used within the hour. There is no vinegar, no sugar, no turmeric, and no oil, and the absence of acid is the reason it is so aggressively hot: nothing halts the enzymatic reaction early, so the full volatile force of the allyl isothiocyanate develops and then, being volatile, disappears. A pot of karashi made in the morning is worth very little by the afternoon, which is why it is mixed in tiny quantities as needed.
It is used as a sharp point rather than a spread: a smear beside tonkatsu, a dab on oden, the sachet that comes with a pack of nattō, a dot on shumai, and stirred into the dressing for karashi-ae vegetables.
The dish that makes the most of it is a Kumamoto speciality with a good story attached. Karashi renkon is lotus root with its holes packed full of mustard mixed into miso, coated in a turmeric-yellow batter and deep-fried, then sliced across so that each round shows a wheel of yellow. It is supposed to have been devised in the 1630s by a monk for the Hosokawa lord of Kumamoto, whose health was poor and whose appetite needed provoking, and the family is said to have kept the recipe secret for two centuries. Sliced and eaten cold, it is one of the sharpest things in Japanese cooking.
Munich, Düsseldorf & the German Lands — c. 1800 CE
Germany eats more mustard per head than almost anywhere in Europe and makes it in more distinct regional styles than anywhere at all.
The extremes sit at opposite ends of the country. Düsseldorf makes a fierce, dark, vinegar-sharp mustard, sold in a stoneware crock and known through the Löwensenf brand; Bautzen in Saxony makes a medium one that carried an entire East German identity through forty years of separation and is still bought out of loyalty. Between them are Bavarian, Franconian, and Swabian styles, each with a fixed sausage to accompany.
The most particular is the sweet one, and it exists because of a single sausage. Weisswurst is a pale veal and pork sausage made fresh in the morning, poached rather than fried, and by Munich tradition eaten before the noon bell. It is delicate and faintly lemony and an ordinary sharp mustard flattens it entirely. Johann Conrad Develey, a Munich mustard-maker, produced süßer Senf in 1854 to solve exactly that problem: coarse-ground brown mustard, mildly heated, sweetened with sugar and caramelised sugar syrup so the result is brown, grainy, and closer to a chutney than a condiment. The pairing has been fixed ever since, and ordering one without the other in Bavaria is treated as an error rather than a preference.
German mustard also goes into cooking in ways French mustard does not: into the sauce for Königsberger Klopse, into potato salads, into the pot of Grünkohl mit Pinkel in the north, and into the glaze on a roast joint.
Sarepta & the Lower Volga — 1810 CE
The fiercest table mustard in Europe comes from a Moravian missionary colony on the Volga steppe, and it exists because somebody was looking for cooking oil.
Sarepta, south of what is now Volgograd, was founded in 1765 by the Moravian Brethren under a charter from Catherine the Great. The steppe around it grew a wild brown mustard, and from about 1801 a colonist named Konrad Neitz began pressing its seed for oil and grinding the residue for the table. The strain became known as Brassica juncea var. sareptana, Sarepta mustard, and within a few decades it was supplying the whole Russian Empire; by the later nineteenth century Sarepta oil was on the imperial table and the mill was one of the largest in the country.
Russian mustard is made from that strain and is startling to anyone expecting Dijon. It is ground from high-sinigrin brown seed, mixed with vinegar, a little sugar, and characteristically a spoonful of the mustard oil itself, and it is hot in a way that goes straight up the nose and brings tears. It is eaten in quantity with kholodets, with sausage, with black bread and salo, and mixed into the dressing for a herring salad. There is a widely repeated Russian household habit of spreading it on the chest for a cold, which is the medieval mustard plaster surviving as a domestic remedy.
The oil itself matters as much as the paste. Mustard oil remains a standard Russian and Ukrainian cooking fat and a baking fat, and it is what a proper borodinsky loaf is brushed with.
Stockholm & Skåne, Sweden — c. 1850 CE
Scandinavia took its mustard from Germany, by way of the Hanseatic trade and the German merchant communities of the Baltic ports, and then sweetened it and married it to fish.
Swedish mustard is coarse, dark, and noticeably sweet, closer to the Bavarian style than to the French, and it is used with a directness that other cuisines reserve for salt. It goes with the Christmas ham, where a mustard and breadcrumb crust is standard; into senapssill, one of the several dressed herrings on a smörgåsbord; alongside ärtsoppa, the yellow pea soup eaten on Thursdays with a spoonful stirred in; and into the sausages that are the country's street food.
Its finest use is hovmästarsås, literally head waiter's sauce, also called gravlaxsås: sweet mustard beaten with sugar, vinegar, oil, and a great deal of chopped dill into a thick emulsion, and served with gravlax. The pairing is exact rather than decorative. Cured salmon is fatty, soft, and sweet-edged, and it needs something with acid, sharpness, and enough body to sit on it without sliding off; the mustard supplies all three, and the mucilage in the seed is what holds the sauce together without an egg.
Denmark and Norway do much the same with their own versions, and the Danish remoulade, a mild sweet mustard-and-pickle sauce quite unlike the French, is on more or less everything sold from a Copenhagen sausage wagon.
The Carolina Midlands & St Louis, USA — 1904 CE
America produced the mildest mustard in the world and then built two entirely separate traditions on it.
The first is the yellow one. French's Cream Salad Mustard was introduced at the St Louis World's Fair in 1904: made from Sinapis alba, the gentle species, thinned, sweetened, and coloured a startling yellow with turmeric, and sold beside a hot dog. It was designed to be inoffensive and it succeeded so completely that for most of the world American mustard now means that colour. Purists are rude about it, but it is doing a specific job well, since the non-volatile heat of white mustard sits on the tongue and does not attack, which is exactly what is wanted on a frankfurter eaten in a crowd.
The second is far older and much more interesting. The midlands of South Carolina, in a belt running roughly from Columbia through Orangeburg and Lexington, barbecue pork with a mustard sauce rather than a tomato or vinegar one, and it is the only region in America that does. The sauce is yellow mustard, vinegar, sugar, and pepper, mopped on during a long smoke and served alongside. The usual explanation is settlement: this is the country of eighteenth-century German Palatine immigrants, whose descendants kept a mustard habit their neighbours never acquired, and the surnames on the older barbecue houses, Bessinger, Shealy, Sweatman, support it. It is a piece of German food culture that survived two hundred and fifty years in the Carolina pines with the mustard intact and everything else gone.
Elsewhere mustard is in the coleslaw, in the deviled eggs, on the corned beef, and in the glaze on a holiday ham.
The Casamance & Senegal — c. 1920 CE
The most widely eaten mustard dish in Africa is Senegalese, and it uses a French condiment that arrived with the colonial trade and stayed long after it.
Yassa comes from the Casamance, the region south of the Gambia, and in its classic form, poulet yassa, chicken is marinated for hours in an enormous quantity of onion with lime juice, chilli, and Dijon mustard, then grilled over charcoal, and the marinade is cooked down separately into a thick, sharp, sweet onion sauce and poured back over. It is served with rice, it is on every Senegalese table and in every Senegalese restaurant abroad, and it has spread across West Africa and into the diaspora.
The mustard is not a garnish and cannot be left out. Onion cooked that long turns sweet, and lime alone is too thin against it; mustard supplies the sharpness and the salt at once, and its emulsifying mucilage is what keeps the sauce from separating into oil and juice as it reduces. The result is a dish that is neither French nor pre-colonial but is unambiguously Senegalese.
That is the pattern worth noticing here. Colonial trade left a great many European goods in West Africa that were used once and abandoned; mustard was taken up, given a job no French cook had thought of, and built into a national dish. Dijon is now on the shelf of ordinary Dakar shops, and Senegal is one of the very few places outside Europe where an imported table mustard has become a genuine staple.
