Abstract:

Alkali-soluble proteins extracted from rapeseed meal were fractionated into soluble and insoluble proteins by acid precipitation. The soluble protein was concentrated by ultrafiltration and dialyzed to remove anti-nutrients (such as glucosinolate and phytic acid) and inorganic salts. The distribution of glucosinolate and phytic acid in various rapeseed protein products and the effects of membrane separation and dialysis conditions on contents of glucosinolate and phytic acid in the soluble protein were studied, and the antioxidant activity of the soluble protein was evaluated by DPPH radical scavenging assay. The yield of the precipitated protein was low. So it was necessary to recover the soluble protein. The glucosinolate in rapeseed meal was extracted together with alkali-soluble proteins and was mainly contained in the soluble protein fraction. The content of glucosinolate in the soluble protein could be significantly reduced by membrane separation. The soluble protein, after membrane separation at CF 4 and DV 3, had a glucosinolate content as low as 0.11 mg/g and had certain DPPH free radical scavenging activity. Phytic acid in rapeseed meal could not be effectively extracted with alkali and mainly remained in the residue. It was difficult to separate phytic acid from the soluble protein by membrane separation.

Key words: rapeseed, soluble protein, membrane separation, antioxidant activity