超声波作用于大豆分离蛋白-磷脂复合体系的流变性和拉曼光谱变化

Effect of Ultrasound on Rheological and Raman Spectroscopy Properties of Soybean Protein Isolate-Phospholipid Composite System

研究超声波低功率(100 W)、中功率(300 W)和高功率(450 W)在不同的时间条件下(12、24 min)对大豆分离蛋白-磷脂复合体系结构和功能性质的影响。扫描电子显微镜及流变学实验显示低、中功率超声波处理形成的凝胶结构致密均匀、弹性模量G’较高,且300 W条件下处理24 min时,样品凝胶性质最好。采用光谱学实验验证后发现,大豆分离蛋白-磷脂复合体系构象的变化是影响其凝胶性质的主要因素;拉曼光谱实验结果表明:超声波改变了大豆分离蛋白的二级结构以及色氨酸、酪氨酸所处的微环境,暴露疏水性基团,使其更易与大豆卵磷脂发生疏水相互作用,且低、中功率条件下超声波对大豆分离蛋白和磷脂交互作用的影响较大。超声波功率进一步增大(450 W)使大豆分离蛋白发生不溶性聚集,减弱了与磷脂间的相互作用,复合体系的功能性质随之下降。

The aim of this study was to compare the effects of ultrasonic treatments at three different power levels（150, 300 and 450 W） for different durations（12 and 24 min） on the structural and functional properties of soybean protein isolate（SPI）-phospholipid composite system. Scanning electron microscope observation and rheology experiments showed that ultrasonic treatments at low and medium powers were suitable to generate compact and uniform gel with high elastic modulus. When the ultrasonic condition remained at 300 W for 24 min, the sample showed the best gel properties. It was confirmed that gel properties were influenced by the conformation of soybean protein-phospholipid composite system. Raman spectra showed that ultrasonic treatment could change the secondary structure of SPI. The microenvironment of tryptophan and tyrosine residues was changed at the same time. The interactions between SPI and lecithin easily occurred because of the exposure of hydrophobic groups. Low and medium power ultrasonication had a stronger effect on the composite system. Insoluble protein aggregates occurred when ultrasonic power increased to 450 W, and the functional properties of the composite system decreased because the interactions between soybean protein isolate and lecithin became weaker.