Abstract: In this experiment, soybean peptides were separated by ultrafiltration. How those major ultrafiltration-system parameters affecting the membrane flux were studied. It has showed that the ultrafiltration membrane with 30000 MWCO (Molecular Weight Cutoff) should run 40min for a cycle at 0.12MPa, 40℃ and pH7.0 and under this condition, the membrane flux would be about 19L/m·2h; when the ultrafiltration membrane with 10000 MWCO should run 60min for a cycle at 0.10MPa, <45℃ and natural pH and under this condition, the membrane flux would be about 25L/m2·h; when the ultrafiltration membrane with 5000 MWCO should run 80min for a cycle, at 0.10MPa, <45℃ and natural pH and under this condition, the membrane flux would be about 22L/m2·h. In the end, soybean peptides were separated according to its molecular weight: 13.21% with molecular weight >30000Da; 4.05% with molecular weight 10000～30000Da; 6.41% with molecular weight 5000～10000Da; and 76.11% with molecular weight <5000Da.

Key words: soybean peptides, ultrafiltration, separation, purification