Impact of glycan content on emulsifying and emulsion-stabilizing properties of Maillard-type soy protein isolate-maltodextrin conjugates

Soy protein isolate (SPI) generally does not possess strong emulsifying activity and faces challenges in functioning as an effective food emulsifier. Maillard-type conjugates of SPI and maltodextrin (MD) have exhibited enhanced emulsifying and emulsion-stabilizing properties. While the impact of glycation on protein functionality has been established, the specific role of varying glycan content in modulating emulsifying and stabilizing properties remains an area requiring further investigation. Therefore, this study prepared four Maillard-type SPI-MD conjugates with varying glycan contents (expressed as grams of maltodextrin per 100 g of protein: 12.44 ± 0.60 g/100 g for M0, 8.10 ± 0.19 g/100 g for M1, 4.88 ± 0.25 g/100 g for M2, and 2.21 ± 0.09 g/100 g for M3) using β-amylase. Turbidimetric analysis showed a positive correlation between emulsifying activity and MD content, with all conjugates outperforming native SPI (15.52 ± 0.17), ranging from 16.54 ± 0.18 (M3) to 22.78 ± 1.18 (M0). Furthermore, rheological and droplet size analysis further showed M0 had the highest emulsifying capacity and stability compared to all other conjugates and native SPI. These improvements are likely attributable to increased water solubility, surface hydrophobicity, zeta potential, and flexible tertiary structures in the SPI-MD conjugates. This study provides fundamental insights into how glycan content influences the structure and functional properties of glycated SPI, offering valuable guidance for the rational design of food-grade emulsifiers.