Controlled enzymatic hydrolysis on characteristic and antioxidant properties of soybean protein isolate-maltodextrin conjugates

This study aimed to investigate the effect of limited hydrolysis on conformational and antioxidant properties of soy protein isolate-maltodextrin (SPI-Md) conjugates. Extrinsic fluorescence analysis showed unfolding of the protein molecule and exposure of hydrophobic groups in SPI-Md conjugate hydrolysates. Free amino acid analysis showed that, the contents of hydrophobic amino acids in SPI-Md conjugates increased after hydrolysis. The contents of leucine, isoleucine, phenylalanine increased from 0.32, 0.30 and 0.54 to 1.36, 1.86 and 2.60, respectively, when the hydrolysis degree (DH) gradually increased from 0% to 5.7%. The FT-IR spectrum showed that C = O absorption of the amide group formed by glycosylation continued unabated after limited hydrolysis (DH 2.9%). The glycated SPI products showed good reducing power and superior resistance to lipid oxidation (34%, 12 mg mL^?1), whereas the limit hydrolysates (DH 2.9%) of SPI-Md conjugates showed more ef?cient radical-scavenging capacity (89.5%, at 12 mg mL^?1) and iron-chelation activity (91.3%, at 12 mg mL^?1). Results of this study indicated that, slight enzymatic hydrolysis (DH 0–2.9%) could help partially unfolding the globular structure of SPI-Md conjugates without deteriorating amide bonds and had a positive effect on their antioxidant properties.