AOAC SPIFAN WPC ERP-Final Action Review (Nov. 2017)

2016.15 (Nov. 2017) - WPC-31 MLT-Final Action Review

FOR ERP USE ONLY DO NOT DISTRIBUTE

Introduction Human milk provides optimal nutrition and health benefits for infants and is the golden standard for the development of infant formulas. Whey proteins are a set of globular proteins in animal milk that remain in solution during casein precipitation (Table 2016.15A). In milk-based infant formulas, the ratio of whey protein to casein can be adjusted to around 60:40 in order to bring the protein and amino acid composition of the formulas closer to that of breast milk [1] (the whey protein to casein ratio in cow’s milk is 21:79 [2] ). China National Standard (GB) 10765-2010 [3] stipulates that for the first age infant formula, the whey protein content must be ≥60% of total protein, but there is currently no official analytical method to measure whey protein content. Thus, an accurate and precise analytical method, suitable for routine testing in quality control labs, was needed to effectively monitor the whey protein content in infant formulas and demonstrate compliance with regulatory standards. An SDS-CGE (Sodium Dodecyl Sulfate – Capillary Gel Electrophoresis) method for determination of whey protein content in infant formula powders was developed and underwent a comprehensive single laboratory validation (SLV) study using a group of commercial infant formulas with known whey protein content (n=41). Method performance met the standard method performance requirements (SMPR) of AOAC [4] . In September 2016, the SDS-CGE method was reviewed by the SPIFAN expert review panel (ERP), approved for Official First Action Status as AOAC Official Method 2016.15 [5] , and recommended to advance to multi-laboratory testing (MLT) study for evaluation of reproducibility. Multi-Laboratory Testing Study The participating laboratories (Table 2016.15B) included government labs (5), infant formula manufacturers (7), university research labs (1), and instrument suppliers (6). Data were obtained using seven different instrument models from four different manufacturers. Prior to the commencement of the MLT study, each collaborator received the method together with a detailed study protocol (approved by members of the SPIFAN ERP) to allow familiarization with the technique and an opportunity to communicate any questions and difficulties. Some analysts also participated in a method training course where the method was demonstrated and questions answered. Two formula samples with known protein content (calculated from the formulation and determined by this method) manufactured by Wyeth Suzhou were used as practice samples. The two practice samples were sent to each lab for testing prior to commencing official multi laboratory testing. After approval of the results by the study director, five selected SPIFAN samples from the SPIFAN kit II (the formula powder samples containing only intact milk proteins) and ten formula samples purchased from the Chinese market (containing different type and content of whey proteins based on product information) were sent to the qualified participating laboratories for analysis.