Rapid aqueous extraction of mucilage from whole white mustard seed David T. Balke, Levente L. Diosady * Department of Chemical Engineering and Applied Chemistry, University of Toronto, 200 College St., Toronto, Ontario, Canada M5S 3E5 Received 1 October 1999; accepted 31 January 2000 Abstract Yellow or white mustard mucilage, present on the surface of Sinapis alba seeds, causes major diculties in the separation of the oil during aqueous processing due to its eectiveness as an emulsi®er. A rapid, ecient aqueous extraction process for the removal of the mucilage from the whole seeds prior to grinding and oil separation has been developed and demonstrated on 1 and 5 l scales. A two-stage extraction process using water with an initial temperature of 45 C at an 8:1 water to seed ratio resulted in over 90% mucilage removal in approximately 3 h. Mucilage removal signi®cantly reduced the water requirement for aqueous oil separation. A three-parameter mathematical model, based upon mass transfer considerations and diminishing mucilage layer thickness, was developed and shown to ®t the bulk phase mucilage concentration data during extraction. Concentration data from many dierent experimental conditions were shown to superimpose when time scaling factors were employed. # 2000 Elsevier Science Ltd. All rights reserved. Keywords: Mustard; Processing; Mucilage; Gums; Aqueous extraction; Modelling; Emulsi®ers; Sinapis alba; Brassica alba; Brassica hirta 1. Introduction Yellow or white mustard (Sinapis alba L.) is com- monly grown for the use of its seed as a spice. While the greens are edible and rather tasty, the agronomic value of the plant lies in the seed. It grows well in the Canadian prairies, making Canada the number one exporter of mustard seed in the world. The seed, as in other cruci- ferae, grow within seedpods, each of which contains 4±8 small (1±1.5 mm diameter) seeds. The seed is high in protein (27%) and oil (31%) and low in starch. The seed coat accounts for approximately 20% of the seed weight. In the maturation of the seedpod, the seeds grow within a jelly-like substance. As the seeds mature, the mucilage dries onto the outer hull of the seeds. The level of mucilage on mustard seed is exceptionally high com- pared to its cousins rapeseed and canola. This mucilage not only gives mustard its superior drought resistance, but is also responsible for the excellent emulsifying and suspension properties of ground mustard. The mucilage is a heterogeneous polysaccharide of a 1,4-linked b-d- glucan (similar to cellulose but more branched) and a pectic material made up primarily of galactose, man- nose, rhamnose, and galacturonic acid (Cui, 1997; Cui, Eskin & Biliaderis, 1993a,b; Weber, Taillie & Stauer, 1974). The mucilage accounts for approximately 5% of the mass of the whole seed, corresponding to 25% of the mass of the hulls. The mucilage forms a hydrogel surrounding the seed when it is wetted. While mucilage may be dissolved into aqueous solution, it has a great anity for the seed and its removal requires several extractions. Cui et al. (1993a) have reported recovery of 5% of the mustard seed mass as ethanol precipitable mucilage via a series of 5 sequential extractions without pH modi®cation, each involving a 25 min extraction at 75 C and a 16 h leaching at 25 C. The seed was sepa- rated from the extraction liquor by ®ltration through cheesecloth. The authors did not indicate whether they applied pressure to express the interstitial water. The mucilage acts in a similar manner to poly- saccharide gums such as glucomannans and pectins. The mucilage is very eective at increasing the viscosity of solutions at levels as low as 0.5±1% w/w. There is 0963-9969/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved. PII: S0963-9969(00)00055-7 Food Research International 33 (2000) 347±356 www.elsevier.com/locate/foodres * Corresponding author. Tel.: +1-416-978-4137; fax: +1-416-978- 8605. E-mail address: diosady@chem-eng.toronto.edu (L.L. Diosady).