Ultrasonic treatment affects emulsifying properties and molecular flexibility of soybean protein isolate-glucose conjugates

The molecular flexibility and emulsifying properties of soy protein isolate (SPI) and soy protein isolate-glucose (SPI-G) conjugates after ultrasonic treatment were studied. The results showed that the degree of Maillard reaction increased significantly with the increase of ultrasonic intensity (P < 0.05), and the flexibility of SPI-G conjugates increased significantly (P < 0.05). After ultrasonic treatment, the particle size of the protein was reduced and the protein structure became looser. The analysis of the fluorescence and FT-IR spectra showed that both the ultrasonic treatment and Maillard reaction process could stretch the structure and increase the flexibility of SPI molecules. Correlation analysis indicated that the molecular flexibility of SPI and SPI-G conjugates treatment after ultrasonic treatment was significantly correlated with protein emulsification activity and emulsion stability.