© Denzil Green
Dijon Mustard is a style of mustard originally made in Burgundy, France. It is named after the city of Dijon, which is the capital of Burgundy.
90% of all mustard made each year in France is Dijon or Dijon-style. 70% of that actually is made in the Dijon area. [Ed: the other major mustard category in France is “moutarde à l’ancienne”; see entry on Grainy Mustards.]
There is no one single brand; some brands of Dijon are milder, some are hotter.
The European Union has ruled that the term “Dijon Mustard” has become generic, rendering it ineligible for a European-wide food protection law. All brands of Djion are, however, made under the terms of a law passed in 2000 governing various mustards in France (originally passed in 1937, amended in 2000. ) The law specifically mentions Dijon, stating that brown or black mustard seed must be used for the product to be referred to as mustard; if white seeds are used, it must be referred to as a condiment. The acidic liquid used can be wine, vinegar (wine vinegar or cider vinegar), or verjuice.
Note though that the law does not mention where Dijon Mustard must be made. Dijon Mustard can be legally made anywhere in France, provided that the rules about ingredients and techniques are followed.
Nor does the law mention where the mustard seed must come from. The seed used can come from anywhere, and indeed 90% of the mustard seed used is imported from Canada. The yellow-flowered fields seen around Dijon are actually rapeseed plants, not mustard plants. Farmers in the Dijon area switched to growing rapeseed as they could make more on rapeseed from EU subsidies than they could growing unsubsidized Mustard Seed.
The seeds are crushed and ground, sieved to get the husk out, then mixed with water, and vinegar or verjuice. Wine vinegar, which makes the mustard a bit more pungent, is more often used. Verjuice gives it a softer edge instead. After this, seasonings such as salt, summer savory, tarragon, and lavender may be added. Ground turmeric may be included for colouring. The mixture is allowed to stand for 3 days, then it is bottled.
Banned from the mustard are the following items: artificial colour or additives, cereal-based flours, and any ingredient aside from mustard seed which tastes similar to mustard (to ensure that the mustard flavour comes purely from the mustard seed itself.) No flavoured variations — e.g. truffle, honey, etc — are allowed. They can be made, but can’t call themselves Dijon Mustard. 
Some well-known brands are Amora, Maille and Grey-Poupon.
Grey-Poupon today in France is made only for export in small quantities. Grey-Poupon mustard sold in America, though, may not be the “real” thing. Rights to the name in America were purchased in 1946 by the Heublein company, which later sold the American rights to the name “Grey-Poupon Dijon Mustard” to Kraft.
Maille brand Dijon Mustard
© Denzil Green
The Romans brought mustard plants to the area, as indeed they did to all of France. Dijon was already a mustard “hot spot” if you will during the Roman period, as the area had many vineyards that could supply the sour grape juice (see entry on verjuice.)
The practice of using verjuice to make a less-acidic type of Dijon Mustard is credited to a man named Jean Naigeon, who reputedly starting doing it in 1752, though there is no documented proof of this exact date or that he did it. The Naigeon family were big in mustard in Dijon at the time; their main mustard rivals were the Maille family in Paris.
The making of Dijon Mustard has been regulated since at least 1390. The 1390 regulations stated that it had to be made from a paste made of mustard seed and good quality wine aged for at least 12 days. Dijon Mustard used to be made from Black Mustard Seed only.
 The regulations govern all mustards,but mention Dijon specifically:
Art. 3. – La dénomination « moutarde de Dijon » est réservée à la moutarde obtenue par le broyage des seules graines de moutarde provenant soit de la variété Brassica nigra, soit de la variété Brassica juncea, tamisées ou blutées, et non déshuilées ; la quantité de téguments résiduelle ne peut excéder 2 % en poids du produit fini.
En outre, la moutarde de Dijon doit satisfaire aux exigences suivantes :
– la teneur en extrait sec provenant des graines de moutarde doit être d’au moins 22 % en poids du produit fini et la teneur en lipides provenant de graines de moutarde d’au moins 8 % en poids du produit fini ;
– elle doit être exclusivement fabriquée à partir d’un liquide de dilution constitué d’un ou de plusieurs des liquides suivants, éventuellement additionnés d’eau, pour autant que l’eau n’excède pas les trois quarts du mélange : vinaigres de fermentation, de vin, d’alcool et de cidre ; jus de raisins verts ; jus et moût de raisin ; vins ;
– elle peut contenir des préparations aromatisantes et des substances aromatisantes naturelles, à l’exception de celles à flaveur moutarde, en particulier contenant de l’allyl isothiocyanate ; l’incorporation de tout autre arôme est interdite ;
– les additions de téguments et de farines de céréales sont interdites.
— “Décret no 2000-658 du 6 juillet 2000 pris pour l’application du code de la consommation relatif aux dénominations des moutardes.” Retrieved September 2011 from http://www.legifrance.gouv.fr/affichTexte.do?cidTexte=JORFTEXT000000218338&fastPos=1&fastReqId=1253768851&categorieLien=id&oldAction=rechTexte
Il n’est moutarde qu’à Dijon? Musée de la Vie bourguignonne. Dijon, France. Juin 2005. Page 3. Retrieved September 2011 from http://www.musees-bourgogne.org/fic_bdd/dossiers_fichier_pdf/1119521833.pdf
Platt, Will. Dijon Mustard Makers in a Jam Over Seeds. Los Angeles Times. 8 June 1996.
Sertl, William. Avez–Vous du Vrai Poupon? Saveur Magazine. 13 February 2007.