Abstract:

The neutral protease-catalyzed hydrolysis products of black soybean protein isolate (BSPI) were fractionated using ultrafiltration membrane with the molecular weight cut-off (MWCO) of 10, 6 and 2 ku. Effects of 4 ultrafiltration parameters, including membrane module type, operating pressure, and pH value and concentration of BSPI peptide solution on membrane separation efficiency, as well as cleaning effects of different reagents on membrane (represented by water flux recovery, WFR), were investigated. Furthermore, hydroxyl radical scavenging activities of BSPI peptides with different MWs were assayed. The results showed that a satisfying ultrafiltration effect was achieved using modified PES flat sheet ultrafiltration membrane module under the conditions of 0.25 MPa, pH 6.5, 2% peptide concentration, and 25 ℃, and the sequential cleaning procedure with proteinase liquid and alkali solution containing SDS and NaClO led to a WFR of 95.68%. Radical scavenging assay indicated that the peptides with MWCO less than 2 ku possessed higher antioxidant capacity and the IC50 was 0.587 mg/ml.

Key words: black soybean, ultrafiltration, antioxidant peptides, membrane cleaning, hydroxyl radical