Extraction and characterization of protein fractions from Australian canola meals

Canola proteins were sequentially extracted from four Australian canola meals of different species and two industrial meal samples, according to Osborne method (OSB), based on their solubilities in water, 5% NaCl, 0.1 M NaOH and 70% ethanol respectively. These extracts were then compared to the glutelin fraction obtained by direct alkaline extraction method (DIR) in terms of protein yield, recovery, electrophoretic profile, and residual antinutritional components. The OSB method was found to be more effective for protein extraction which resulted in higher cumulative protein yield and recovery of water-soluble protein fractions, although the DIR method produced a glutelin fraction of higher protein content. Phenolic compounds were observed in all the extracted protein fractions although sinapine, the major phenolic compound in canola, was present only in the albumin fractions. The glucosinolate content of all extracts was below the detection limit of the method employed (< 3 μmol/g). While the electrophoretic profiles of all four OSB fractions were largely different, the DIR fraction was very similar to the glutelins obtained from the OSB method. Isoelectric focusing revealed that many of the proteins in the canola varieties ranged in pI between pH4.6 and 8.3.