J Agric Food Chem. 2015 Jan 14;63(1):297-303. doi: 10.1021/jf5056024.
Beta-lactoglobulin (BLG)–catechin conjugates were prepared by a free radical method and investigated with sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), electrospray ionization–mass spectrometry (ESI-MS), and far-UV circular dichroism (CD). Covalent binding between BLG and catechin were confirmed with SDS-PAGE and ESI-MS. About 93% of beta-lactoglobulin was conjugated with catechin or catecin fragments according to the gel intensity analysis software. Far-UV CD results showed that the content of β-sheet decreased with a corresponding increase in unordered structures after grafting. Both nanoemulsions with mean particle size between 160 and 170 nm were prepared. Both the rate of particle growth and the total beta-carotene (BC) loss at 50 °C were significantly greater than at 4 and 25 °C. The retention rates of BC in nanoemulsions were 27.8% and 48.6% for BLG and BLG–catechin conjugates, respectively, after 30 days of storage at 50 °C. The BC retention encapsulated in nanoemulsion was significantly improved using BLG–catechin conjugates, compared with BLG alone. The increase of BC retention in nanoemulsions encapsulated with BLG–catechin conjugates was due to the significant improvement of antioxidative properties (reducing power, free radical scavenging activity, and hydroxyl radical scavenging activity) of BLG after covalent binding with catechin. The results indicated that the proteins modified with polyphenols can be widely used in a labile bioactive compounds encapsulation delivery system.
β-乳球蛋白（BLG）-儿茶素缀合物通过自由基方法制备，并通过十二烷基硫酸钠聚丙烯酰胺凝胶电泳（SDS-PAGE）、电喷雾电离-质谱（ESI-MS）和远紫外圆二色性（CD）进行了研究。通过 SDS-PAGE 和 ESI-MS 证实了 BLG 和儿茶素之间的共价结合。根据凝胶强度分析软件，约 93%的β-乳球蛋白与儿茶素或儿茶素片段缀合。远紫外 CD 结果表明，接枝后β-折叠结构的含量降低，无规结构相应增加。均制备了平均粒径在 160-170nm 之间的纳米乳液。在 50°C 时，粒子生长速度和总β-胡萝卜素（BC）损失均明显大于在 4°C 和 25°C 时。在 50°C 下储存 30 天后，BLG 和 BLG-儿茶素缀合物包封的 BC 保留率分别为 27.8%和 48.6%。与 BLG 相比，BLG-儿茶素缀合物显著提高了纳米乳液中 BC 的保留率。BLG-儿茶素缀合物包封的纳米乳液中 BC 保留率的增加归因于儿茶素共价结合后 BLG 抗氧化性能（还原能力、自由基清除活性和羟基自由基清除活性）的显著提高。结果表明，经过多酚修饰的蛋白质可以广泛应用于不稳定生物活性化合物的包封传递系统。
