Relationship between Molecular Flexibility and Emulsifying Properties of Soy Protein Isolate-Glucose Conjugates

At present, the structure–activity relationships of soy protein isolate are still not well understood. In this paper, the relationship between molecular flexibility and emulsifying properties of soy protein isolate and soy protein isolate–glucose conjugates were investigated. The Maillard reaction was carried out at different temperature conditions (50 °C, 60 °C, 70 °C, 80 °C, and 90 °C) under a specific wet condition. Meanwhile, structural properties including surface hydrophobicity (H0), molecular flexibility and secondary, tertiary, quaternary structures, and the free sulfhydryl group (−SH) content were measured. The results showed that there was a good correlation between molecular flexibility and emulsifying properties, and the correlation coefficients was 0.920 (P < 0.01) for emulsifying activity and 0.952 (P < 0.01) for emulsion stability. Compared with soy protein isolate, the H0 of samples at different temperatures first increased and then decreased reaching a maximum at 70 °C, a red shift occurr...