Electrophoretic and functional properties of mustard seed meals and protein concentrates

Defatted meals and protein concentrates from five varieties of mustard seeds (four Brassica spp. and one Sinapis alba) were analyzed for polypeptide composition and functional properties. Nonreducing gel electrophoresis showed that Brassica seeds lacked the 135- and 50-kDa polypeptides that were present in the seeds of the S. alba variety. On the other hand, the 29-kDa polypeptide found in the Brassica seeds was absent from the seed of the S. alba variety. Under reducing conditions, the 135 kDa was not detected in the S. alba variety and the intensity of the 50-kDa polypeptide was severely reduced; in contrast, the intensity of the 29-kDa polypeptide in the Brassica seeds was not affected. Meals from yellow seeds had significantly higher (Pless than or equal to0.05) protein contents than meals from the brown seeds. The emulsifying activity indexes (EAI) of meals and protein concentrates from the Brassica seeds were significantly higher (Pless than or equal to0.05) than those obtained for similar products from S. alba seeds. It was concluded that the disulfide-bonded 50- and 135-kDa polypeptides may have contributed to increased rigidity of S. alba meal proteins, which resulted in poor EAI when compared to the Brassica meals, which do not contain these polypeptides.