热加工处理对β-乳球蛋白与茶多酚间相互作用的影响

Interaction of β-lactoglobulin with tea polyphenols under different thermal processing

利用荧光光谱技术分析β-乳球蛋白与EGCG、EGC间的相互作用,通过测定其结合常数、结合位点数、热力学常数及β-乳球蛋白的构象变化,探究不同热处理加工条件(80℃/20 min、100℃/5 min)和加热方式(蛋白与茶多酚混合加热、蛋白单独加热)对β-乳球蛋白与茶多酚间相互作用的影响。结果表明,热加工处理对β-乳球蛋白构象及与EGCG、EGC的结合强度有不同影响。β-乳球蛋白热变性致结构展开,从而表现出与EGCG、EGC的结合能力增强。EGCG、EGC均能与β-乳球蛋白自发形成复合物而发生相互作用,结合强度EGCG明显大于EGC。对比EGCG、EGC与β-乳球蛋白混合加热和β-乳球蛋白单独加热,发现80℃混合加热后的结合强度均大于80℃蛋白单独加热,分别增加55.56%和42.78%,而100℃混合加热后的结合强度均小于100℃蛋白单独加热,分别减小14.44%及74.22%。热加工处理能改变EGCG、EGC与β-乳球蛋白的结合力类型。

Tea polyphenols are rich in catechins, and epigallocatechingallate （EGCG）, and epigallocatechin （EGC） are typical cateehins monomer. The competitive interactions of β-lactoglobulin with EGCG and EGC under the two heat processing conditions （80 ℃/20 min; 100 ℃/5 min） and two heating methods （heating the mixture; protein alone heating） were investigated by fluorescence spectroscopy. The influence of heating process and conditions on the interaction between β-lactoglobulin and tea polyphenols was studied by measuring binding constant, binding sites, thermodynamic parameters and conformational changes of β-lactoglobulin. The results indicated that the thermal processing changed the structure of β-lactoglobulin and the binding ability of EGCG/EGC with β-lactoglobulin. The structure of β-lactoglobulin were more open than its native state due to the heat-induced denaturation and unfolding of protein. Therefore, the strong binding affinity with EGCG and EGC were observed. The β-lactoglobulin can spontaneously interact with EGCG/ EGC to form a complex and its binding strength with EGCG was stronger than that with EGC. Compared with heating mixing EGCG, EGC and β-lactoglobulin and heating with β-lactoglobulin alone, it was found that after 80℃ mixed heating, the binding strength were stronger than that of protein alone heating, and binding strength was increased by 55.56% and 42.78% respectively. However, after 100℃ mixed heating, the binding strength were weaker than 100℃ protein alone heating, decreased by 14.44% and 74.22% respectively. Thermal processing can change binding types of EGCG/EGC with β-lactoglobulin.