β-乳球蛋白对VE热稳定性的影响

为改善超高温瞬时灭菌（ultra-high temperature instantaneous sterilization，UHT）乳中VE的热稳定性，以β-乳球蛋白（β-lactoglobulin，β-LG）和VE为材料制备复合物，探究β-LG对VE热稳定性的影响。通过浊度、粒径、Zeta电位、扫描电子显微镜、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳、红外光谱和荧光光谱研究β-LG与VE的结合情况；利用生物膜干涉技术进一步分析β-LG与VE之间的结合程度；通过高效液相色谱法测定普通强化乳（添加VE）和复合物强化乳（添加β-LG/VE复合物）中UHT前后的VE含量并计算VE热损失率，以确定β-LG对VE热稳定性的影响。结果表明，β-LG可以通过氢键和疏水相互作用与VE结合形成复合物，β-LG与VE结合后，可以减少VE在水溶液中的聚集，使VE的溶解性增加；生物膜干涉技术也证明β-LG与VE之间存在结合，亲和力常数为7.493×10－2?mol/L；复合物强化乳中VE损失率为（4.01±0.18）%，显著低于普通强化乳（（10.90±0.17）%）（P＜0.05）。以上说明，β-LG可以显著提高VE的热稳定性，为开发维生素强化乳制品提供理论基础。

Effect of β-Lactoglobulin on the Thermal Stability of Vitamin E

In order to improve the thermal stability of vitamin E (VE) in ultra-high temperature sterilized (UHT) milk, a complex of β-lactoglobulin (β-LG) with VE was prepared. Turbidity, particle size, zeta potential, scanning electron microscopy, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), infrared spectroscopy and fluorescence spectroscopy were used to explore whether β-LG combined with VE. The degree of binding was further analyzed by bio-layer interferometry. The contents of VE in common fortified milk (with VE) and complex fortified milk (with β-LG/VE complex) before and after ultra-high temperature sterilization were determined by high performance liquid chromatography (HPLC) and the loss rate of VE was calculated to determine the effect of β-LG on the thermal stability of VE. The results showed that β-LG combined with VE to form a complex through hydrogen bonds and hydrophobic interaction, and that binding to β-LG reduced the aggregation of VE in aqueous solution and increased its solubility. Bio-layer interferometry corroborated the binding between β-LG and VE, and the binding constant was 7.493 × 10-2 mol/L. The loss rate of VE in complex fortified milk was significantly lower than that in common fortified milk, (4.01 ± 0.18)% versus (10.90 ± 0.17)% (P < 0.05). The above results showed that β-LG/VE could effectively improve the thermal stability of VE, which provides a theoretical basis for the development of vitamin fortified dairy products.