Feng Ping, Fuerer Christophe, McMahon Adrienne
Wyeth Nutrition, 30F, CITIC Square, 1168 Nanjing Rd (W), Shanghai 200041, People's Republic of China.
Nestlé Research Center, Vers-chez-les-Blanc, 1000 Lausanne 26, Switzerland.
J AOAC Int. 2018 Sep 1;101(5):1566-1577. doi: 10.5740/jaoacint.18-0057. Epub 2018 May 31.
A multilaboratory testing study was conducted on AOAC First Action Official Method SM 2016.15: Quantification of Whey Protein Content in Infant Formula Powders by Sodium Dodecyl Sulfate-Capillary Gel Electrophoresis (SDS-CGE). Nineteen laboratories participated in the analysis of duplicate blind-coded samples of 15 formula powder products for infants and young children. Electrophoregrams were recorded at UV220 nm and integrated. The normalized peak areas of whey and casein proteins were summed separately to calculate total whey protein content. Apart from one sample [NIST Standard Reference Material (SRM) 1849a], relative standard deviation of repeatability (RSDr) and reproducibility (RSDR) ranged from 0.83 to 2.11% and from 2.18 to 4.22%, respectively, and Horwitz ratios ranged from 1.02 to 1.85, meeting the precision limits specified in the whey protein Standard Method Performance Requirements and in the guidelines recommended for the Horwitz ratio. In these samples, the measured whey protein content was between 98 and 108% of the declared value. NIST SRM 1849a showed atypical results, with elevated RSDr (3.51%), RSDR (5.94%), Horwitz ratio (2.62), and recovery (134%). There is no clear reason for this. The percent whey protein value for NIST is calculated from the formulation and is not a reference or certified value. Multiple instrument models and makes, as well as capillary sources, were used in this collaborative study, demonstrating the robustness of the method. The method is fit-for-purpose for the quantification of whey protein content in milk-based formula powder products for infants and young children. It is not applicable to the analysis of hydrolyzed or plant protein-based infant formulas.
针对美国官方分析化学师协会（AOAC）首次采用的标准方法SM 2016.15：通过十二烷基硫酸钠 - 毛细管凝胶电泳（SDS - CGE）定量婴幼儿配方奶粉中的乳清蛋白含量，开展了一项多实验室测试研究。19个实验室参与了对15种婴幼儿配方奶粉产品的双份盲编码样品的分析。在紫外220nm处记录电泳图并进行积分。分别对乳清蛋白和酪蛋白的归一化峰面积求和，以计算总乳清蛋白含量。除了一个样品 [美国国家标准与技术研究院（NIST）标准参考物质（SRM）1849a] 外，重复性相对标准偏差（RSDr）和再现性相对标准偏差（RSDR）分别在0.83%至2.11%和2.18%至4.22%之间，霍维茨比率在1.02至1.85之间，符合乳清蛋白标准方法性能要求及霍维茨比率推荐指南中规定的精密度限值。在这些样品中，测得的乳清蛋白含量为申报值的98%至108%。NIST SRM 1849a显示出非典型结果，RSDr（3.51%）、RSDR（5.94%）、霍维茨比率（2.62）和回收率（134%）均升高。对此尚无明确原因。NIST的乳清蛋白百分比值是根据配方计算得出的，并非参考值或认证值。本协同研究中使用了多种仪器型号、品牌以及毛细管来源，证明了该方法的稳健性。该方法适用于定量婴幼儿乳基配方奶粉产品中的乳清蛋白含量。它不适用于水解或植物蛋白基婴幼儿配方奶粉的分析。
