Enhancing the Emulsifying Properties of Soybean Protein in Acidic Conditions by Ultrasound-enzymatic Modification
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Abstract:
In order to study the effect of ultrasound-enzymatic modificationon the emulsifying properties of soybean protein isolate (SPI) under acidic conditions (pH 4), SPI was used as the raw material in this study. The emulsifying properties and particle sizes were used as evaluating indices to determine the optimum conditions for the modification method using ultrasound combined with phytase-acidic protease (Uphy-aci). The results showed that, when the SPI concentration was 6%, the amount of phytase was 4 U/g, that of the acid protease was 1500 U/g, and the durations of enzymatic hydrolyses using phytase and acidic protease were 50 min and 30 min, respectively. The emulsion performance was significantly increased and the size of the emulsion particles decreased. The surface hydrophobicity, H0, and the scanning electron microscope (SEM) were used to analyze the structure of SPI under the optimal Uphy-aci conditions. The surface hydrophobicity of SPI was 487.78 under acidic conditions and was enhanced by 71.2% compared to that of the unmodified sample. Moreover, SPI presented a homogeneous and porous microstructure. Therefore, the ultrasound-enzymatic modification method can effectively improve the emulsifying properties and functional properties of SPI in acidic conditions, and expand the applications of SPI.
