Ultrafiltration to fractionate wheat polypeptides

An ultrafiltration process allowing the fractionation of two kinds of polyp eptides issued from limited chymotryptic hydrolysis of wheat gliadins was a pplied to wheat gluten hydrolysates. Hydrophilic and poorly charged polypep tides were well transmitted through an inorganic ZrO2-based membrane at aci dic pH, whereas hydrophobic and positively charged polypeptides were highly retained. By combining reversed-phase and cation-exchange chromatography ( CEC), it was proved that the fractionation of the polypeptides was based on electrostatic repulsion of the charged polypeptides by the positively char ged membrane. After a continuous diafiltration process, retentates containi ng 75 to 88% of hydrophobic polypeptide and permeates containing 84 to 90% of hydrophilic polypeptides were recovered, depending on the size of membra ne used. Even if the ultrafiltration fractions were less purified than frac tions issued from CEC, it was shown that they exhibited very different foam ing properties: permeate did not produce nor stabilize foams, whereas reten tate was more efficient than the whole hydrolysates and BSA. (C) 2001 Elsev ier Science B.V. All rights reserved.