Isolation of faba bean legumin — a comparative study of various methods

Different methods of legumin isolation from faba beans were compared with regard to the removal of vicilin taking into consideration the additional influence of variety. SDS-PAGE, analytical ultracentrifugation and SE-HPLC were used for the analysis of protein composition. SDS-PAGE analysis of the isolated legumin samples revealed, that neither combined salt fraction/isoelectric precipitation nor heating to 73 °C resulted in a complete removal of vicilin. Time-consuming isoelectric zonal precipitation and heating at 83 °C as described by Schlesier et al. (Biochem. Physiol. Pflanzen 180 (1985) 225) provides legumin preparations free of vicilin in low yields. Acceptable yields in shorter time were obtained by combining isoelectric precipitation/salt fractionation with Schlesier's procedure. SDS-PAGE analysis showed a certain dependence on variety of the patterns of legumin α-polypeptide chains.