Abstract:In this study, soybean protein isolate and four polysaccharides (carrageenan, xanthan gum, flaxseed gum, guar gum) were used as the raw materials for preparing soy protein isolate-polysaccharide complex. The turbidity, surface hydrophobicity, emulsifying activity and emulsified emulsion stability of the complex were evaluated, and the soy protein isolate-carrageenan complex was determined to have better physicochemical properties, which was used for the optimization of the subsequent ultrasonic-assisted preparation conditions. The effects of different pH values (2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0), ultrasonic power (200, 400, 600, 800 W) and ultrasonic time (2, 4, 6, 8, 10 min) on the structure and properties of proteinpolysaccharide complexes were investigated. Fluorescence spectra were used for exploring the structural characteristics of the complex, and the physico-chemical characteristics of the complex were determined based on turbidity, surface hydrophobicity, particle size and potential. The results showed that a stable soy protein isolate-carrageenan complex was formed when the mass fraction of carrageenan was 0.1%, pH value was 7.0, ultrasonic power was 400 W, and ultrasonic time was 4 min. The complex had the maximum turbidity of 0.44, the maximum surface hydrophobicity of 285.15 μg, the minimum particle size of 139.06 nm, and the maximum absolute potential of 27.23 mV. This study provides a theoretical support for the subsequent research on protein-polysaccharide emulsion gel as a fat substitute.
