【摘要】 β-酪蛋白（β-CN）是牛乳中的主要酪蛋白。它包含13种变异体,其中A2是牛β-CN的主要变异体之一。定量测定A2 β-CN对A2乳制品的评价十分重要。该文建立了对液态奶和奶粉中A2 β-CN及总β-CN分离并定量的毛细管区带电泳（CZE）分析方法。使用熔融石英毛细管（50μm×30/40 cm有效/总长度）,以50 mmol/L Na₂HPO₄+140 mmol/L柠檬酸+0.2%（质量分数） HPMC+4 mol/L尿素溶液（pH为2.7）作为分离缓冲溶液,在214 nm下检测。总β-CN和A2 β-CN的校准峰面积与其质量浓度间呈良好的线性关系,相关系数在0.996 8～0.999 7之间,加标回收率为85.5%～106.4%。对两款巴氏奶和两款奶粉中A2 β-CN和总β-CN进行分析,A2 β-CN和总β-CN的日内精密度分别为2.4%～4.7%和2.6%～4.8%,日间精密度分别为4.0%～6.3%和3.9%～6.7%。所建立的CZE方法可分离液态奶及奶粉中的A2 β-CN,并可对A2 β-CN及总β-CN进行定量。通过计算A2 β-CN在总β-CN中的占比来评价A2乳制品的质量,为保护消费者的利益提供了方法依据。更多还原

【Abstract】 β-casein(β-CN) is one of the major casein proteins in cow milk. There are 13 different variants documented for β-CN in cow milk, among which A1 and A2 are the major variants. The separation and quantitation of A2 β-CN are imperative for A2 dairy products. A new capillary zone electrophoresis(CZE) method with UV detection at 214 nm was established for the separation and quantification of the A2 variant and total β-CN content in cow milk and milk powders. The separation of β-CN variants was achieved on bare fused silica capillaries(50 μm×30/40 cm(effective/total length)). The separation buffer was a mixture of 4 mol/L urea, 0.2%(mass fraction) hydroxypropyl methylcellulose, 140 mmol/L citric acid, and 50 mmol/L disodium hydrogen phosphate buffer(pH 2.7). The corrected peak areas and the concentrations of total β-CN and the A2 variant showed good linearity, with correlation coefficients(r~2) ranging from 0.996 8 to 0.999 7. The intra-day precisions for A2 β-CN and total β-CN determination in four samples(two pasteurized milk samples and two milk powder samples) were in the ranges of 2.4%-4.7% and 2.6%-4.8%, respectively. The inter-day precisions for A2 β-CN and total β-CN determination in four samples were in the ranges of 4.0%-6.3% and 3.9%-6.7%, respectively. The recoveries of A2 and total β-CN ranged from 85.5% to 106.4%. With the established CZE method, the A2 β-CN variant and total β-CN protein in liquid and powder bovine milk products could be separated and accurately quantified. By calculating the A2 β-CN content in the total β-CN, the quality of A2 dairy products can be evaluated, and this in turn would aid in the protection of consumer rights.更多还原