Dijon mustard is simply a prepared mustard made of brown mustard seeds, white vinegar and/or white wine, preservative(s), usually citric acid, turmeric to enhance colour and seasoning(s). The ingredients added will depend on the brand.
There are several brands and styles of Dijon mustard (for example: old fashioned or Old style Dijon, creamy Dijon, original Dijon, honey Dijon, just to mention a few).
Canada is the largest producer and exporter of brown mustard seeds. (Mustard Production for Alberta).
Why is it called Dijon Mustard?
The very original Dijon mustard was made in the City of Dijon in France. The company was started by François Naigeon in 1703 and later registered as “Amora” in 1919. After several changes, the plant was bought by Unilever in 2000, and later closed in 2009, when all production was moved to the neighbouring City of Chevigny-Saint-Sauveur, which is currently the largest production site for European Condiments (Dijon mustard, mayonnaise, gherkins and vinegar) (L’usine nouvelle).
The original Dijon mustard was blended with verjuice. (Wiki Cookbook)
Since Dijon mustard does not have a Protected Designation of Origin, the name is generic, which means mustard can be produced anywhere in the world and be labelled as Dijon mustard.