Effects of maltodextrin glycosylation following limited enzymatic hydrolysis on the functional and conformational properties of soybean protein isolate

The soy protein hydrolysate (HSPI) was first prepared using Neutrase and then glycosylated with maltodextrin (Md) at different incubation times (120, 180, 240, 270, and 300 min). The effect of glycosylation following limited enzymatic hydrolysis on the physicochemical properties of HSPI was investigated. The sodium dodecylsulphate polyacrylamide gel electrophoresis was used to confirm the covalent conjugation and determine the changes in the molecular weight of soybean protein isolate (SPI) during the structural modification. Surface hydrophobicity (H (0)) measurements revealed that limited hydrolysis as well as glycosylation at 120 min increased H (0); however, further glycosylation decreased H (0) due to the shielding effect of the maltodextrin bound. The increased secondary, tertiary conformation stability was confirmed by the far-UV circular dichroism spectroscopy, the intrinsic fluorescence analysis, and the results of differential scanning calorimetry. Subsequently, the functional properties including solubility, heat stability, emulsifying property, as well as antioxidant activities were evaluated. Results indicated that the emulsifying activity index was improved notably from 86.13 +/- A 1.31 m(2)/g for the native SPI to 109.07 +/- A 4.45 m(2)/g for HSPI-Md conjugates after 270-min incubation. Additionally, the glycosylation had obviously positive effects on the antioxidant activities of the modified SPI proteins. Therefore, HSPI-Md conjugates might be used as potential emulsifiers or multifunctional wall materials for the microencapsulation of bioactive ingredients.