This is a three-stage process in which mustard mucilage is extracted from the hulls or bran of yellow mustard seed (sinapis alba). In the first, or pre-purification stage, whole bran and a constant boiling azeotrope are placed in a counter-current extractor, which simultaneously extracts free sugars and mustard oil from the bran. In the second stage the purified bran from the first stage is slurried with water at preferably an elevated temperature, and centrifuged, for instance, to separate the aqueous mucilage from the bran, which may then be dried to form animal feed, or other by-products. In the third stage the mustard mucilage is separated from water in the aqueous solution by flash evaporation or by alcohol precipitation, and the concentrated mucilage is then drum or freeze dried.