为了探究热处理条件下不同pH对乳铁蛋白 (LF)-乳糖复合物的结构与理化特性的作用，对LF-乳糖复合物的浊度、粒径、微观结构和构象进行测定。结果表明：在不同pH（2-10）条件下，LF-乳糖以不同的结构存在。在pH为2和4的酸性环境中，LF和乳糖处于共溶状态，热处理前后溶液浊度没有明显变化，其粒径维持在10 nm左右。在弱酸性和碱性环境中（6-10），LF和乳糖形成复合物，其溶液浊度明显增大，其粒径也从约10 nm增加到约460 nm。扫描电镜（SEM）显示了其结构从零散分布到线性聚集，再到团状聚集的过程。红外光谱（FTIR）显示了复合物形成后的酰胺带和890 cm-1处β-糖苷键的特征峰的变化。圆二色谱（CD）显示α-螺旋随pH增加从20.62%减少到18.23%，β-折叠则逐渐从33.35%增加到37.17%。 SDS-PAGE图谱表明，碱性条件下生成了以非二硫键为主要作用力的聚集体。研究结果拓展了乳铁蛋白在食品中的应用。

The turbidity, particle size, microstructure, fourier transform infrared spectroscopy, circular dichroism chromatography and SDS-PAGE electrophoresis of the LF/lactose complex were measured for determining the structure and characteristics of LF-lactose complex under different pH conditions. The results showed that LF-lactose existed in different forms at different pH. LF and lactose were in a co-solvent state in acidic environment (pH 2 and 4). The turbidity of the solution did not change significantly after heat treatment, and the particle size were maintained at about 10 nm. LF and lactose formed a complex in a weakly acidic and alkaline environment (pH 6-10), it’s particle size increased from 10 nm to 460 nm. Scanning electron microscopy (SEM) showed that the process of the complex structure from scattered to linear aggregation, and then to cluster aggregation. Infrared spectroscopy (FTIR) showed the amide band and changes of characteristic peaks of β-glycosidic bonds at 890 cm-1 after the formation of the complex. Circular dichroism (CD) showed that the α-helix decreases from 20.6% to 18.2% with the increase of pH, and β- folding gradually increased from 33.3% to 37.1%. The SDS-PAGE showed that aggregates with non-disulfide bonds as the main force were formed under alkaline conditions. The results expand the application of lactoferrin in food.

国家自然科学基金面上项目（31972021），广东省自然科学基金重点项目（2018B0303110006），广东省国际合作项目（2018A050506048），广东省重点研发项目（2019B020212003），广东省促进经济高质量发展专项（MEPP[2019]A38），广东省现代农业产业技术体系创新团队建设专项（2019KJ117），广东省农科院人才项目（R2018PY-JX002）。