Analysis of alpha-lactalbumin, beta-lactoglobulin A and B in whey protein powder, colostrum, raw milk, and infant formula by CE and LC

Two analytical methods, capillary electrophoresis (CE) with UV detection and high-performance liquid chromatography (HPLC) with photodiode array detection, were developed for the determination of α-lactalbumin (α-Lac), βlactoglobulin A (β-Lg A), and β-lactoglobulin B (β-Lg B) in whey protein powder, colostrum, raw milk, and infant formula. The CE analysis was performed in a bare fused silica capillary (57 cm×50 μm, effective length 50 cm) with a separation buffer consisting of 0.5 mol L boric acid, 0.025 mol L hydroxypropyl-βcyclodextrin, and 0.8 g L poly(ethylene oxide) 4,000,000 at pH 9.10. The HPLC analysis was performed on a CAPCELL PAK C8 SG 300 (200×4.6 mm, 5-μm particles) column with a gradient mobile phase mixture consisting of acetonitrile and water containing trifluoroacetic acid. The CE method is suitable for the simultaneous determination of α-Lac, β-Lg A, and β-Lg B in whey powder, colostrum, and raw bovine milk, whereas the HPLC method can only be used for quantitative assays of β-Lg A and β-Lg B due to the co-elution of lactoferrin with α-Lac. Recoveries for both methods over the concentration range were between 90.7% and 116.8%. Whey protein powder had the highest content of the above three proteins. The contents of α-Lac in infant formula increased with the raise of age stage. Infant formula with the same age stage but different brands and countries had significant differences in the content of α-Lac. Dairy Sci. & Technol. (2011) 91:213–225 DOI 10.1007/s13594-011-0006-9 X. Ding (*) Y. Yang : S. Zhao Y. Li Beijing Center for Disease Control and Prevention, Beijing 100013, China e-mail: [email protected] Y. Yang : Z. Wang (*) College of Food Science and Technology, Agricultural University of Hebei, Baoding 071001, China e-mail: [email protected] X. Ding : Y. Li Department of Public Health and Domestic Medicine, Capital Medical University, Beijing 100069, China 摘要 本文建立了紫外检测-毛细管电泳 (CE-UV) 及二极管阵列检测-高效液相 色谱 (HPLC) 测定乳清蛋白粉、初乳、原料奶及婴儿配方奶粉中α-乳白蛋白 (α-Lac) 、β-乳球蛋白A (β-Lg A) 及β-乳球蛋白B (β-Lg B) 的新方法 CE法以 石英毛细管柱 (57 cm×50 μm, 有效长度50 cm) 为分离柱、以0.5 mol L硼酸、 0.025 mol L羟丙基β-环糊精及0.8 g L 聚乙烯醇4,000,000为分离缓冲液 (pH 9.10)。HPLC法以CAPCELL PAK C8 SG 300 (200×4.6 mm, 5 μm)为色谱 分离柱, 以含乙腈及三氟乙酸的流动相梯度淋洗方式实现了上述三个蛋白的分 离与测定。CE方法适合于乳清蛋白粉、牛初乳及原料奶样品中α-Lac、β-Lg A 及, β-Lg B的同时分离与测定, 而HPLC法中因乳铁蛋白干扰α-Lac, 仅能定量其 中的β-Lg A 及 β-Lg B。两种方法在测定的浓度范围内回收率在90.7–116.8% 间。乳清蛋白粉中上述三个蛋白的含量最高, 婴儿配方奶粉中α-Lac含量随着 年龄阶段数的增加而增加, 而且同一阶段内不同厂家不同国别婴儿配方奶粉 中α-Lac含量差异也较大。