通过改变浸提温度得到不同茶汤,然后采用紫外-可见吸收光谱、傅里叶变换红外光谱和荧光光谱分析了茶汤、表没食子儿茶素(epigallocatechin,EGC)、表没食子儿茶素没食子酸酯(epigallocatechin gallate,EGCG)对乳清蛋白结构的影响。结果表明,随着浸提温度升高,茶汤中茶多酚浓度增大,EGCG浸出量随浸提温度升高上升明显,而EGC浸出量受浸提温度影响不大。茶汤、EGC、EGCG均能使乳清蛋白的结构发生变化,从而氨基酸残基的微环境发生变化,EGC、EGCG与乳清蛋白相互作用形成复合物。EGC和EGCG都对乳清蛋白有荧光猝灭作用,它们之间是静态猝灭,EGCG的猝灭能力强于EGC。由热力学参数ΔH、ΔS、ΔG可知,EGC、EGCG与乳清蛋白反应是自发进行,它们之间主要是疏水相互作用,EGCG与乳清蛋白的结合力强于EGC。
Different tea soups were obtained by changing the extraction temperature. The influence of tea soup, epigallocatechin (EGC), and epigallocatechin gallate (EGCG) on the structure of whey protein was analyzed by ultraviolet-visible absorption spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectroscopy. Results showed that as the extraction temperature increased, the concentration of tea polyphenols in the tea soup increased. The content of EGCG increased significantly with the increase of the extraction temperature, while the content of EGC was not greatly affected by the extraction temperature. Tea soup, EGC, and EGCG could all change the structure of whey protein, and the microenvironment of amino acid residues changed. EGC and EGCG interacted with whey protein to form a complex. Both EGC and EGCG had a fluorescence quenching effect on whey protein, and the quenching type belonged to static quenching. The quenching ability of EGCG was stronger than that of EGC. According to the thermodynamic parameters ΔH, ΔS, ΔG, the reactions between EGC, EGCG, and whey protein proceeded spontaneously, and they were mainly hydrophobic interactions. The binding force of EGCG and whey protein was stronger than that of EGC.
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