Influence of membrane processing on functional properties of rapeseed protein preparations

The rapeseed protein preparations were obtained by isolation of proteins from the extracted, non-toasted meal by means of the fractionation and enzymatic modification of proteins with utilisation of membrane techniques. Enzymatic hydrolysis of proteins was performed during extraction by means of Alcalase 2.5L in the portion of 9 AU/kg of the substrate protein. To recover and purify the non-precipitating in coagulation regime protein fractions, the membrane techniques were used. The ultrafiltration and diafiltration were performed in the unit for cross-flow ultrafiltration with hollow-fibre membrane cartridges with a nominal molecular weight cut-off range of 20, 70 and 100 kDa, respectively. The influence of the molecular weight cut-off, yield of filtration, concentration factor during ultrafiltration and diafiltration step on the foaming and emulsifying properties of the rapeseed protein preparations was investigated. It has been shown that the application of the membrane cartridges with molecular weight cut-off range of 20 kDa gives relatively the highest recovery of rapeseed "albumin" fraction and by the way it allows obtaining of preparations with better foaming and emulsifying properties. The improvement of properties mentioned above was dependent, to a greater extent, on the diafiltration step than on the concentration factor.