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

Samples were tested over 2 separate days as blind-coded duplicate pairs (both duplicates tested on the same day). The list of testing samples is shown in Table 2016.15C. All data were statistically analyzed using the AOAC harmonized guidelines for collaborative studies to establish overall mean, intra-laboratory repeatability (S r ), relative standard deviation of repeatability (RSD r ), inter-laboratory reproducibility (S R ), relative standard deviation of reproducibility (RSD R ), and Horwitz ratio (HorRat) [6] . Cochran ( p =0.025, one-tail) and Grubbs (single and double, p =0.025, two-tails) tests were utilized to highlight outliers, but all values were kept for statistical evaluation. Upon successful completion and review of the data, in September 2017, the AOAC ERP recommended approval of AOAC Official Method 2016.15 for official Final Action Method status. Method The method protocol sent to the collaborating laboratories was as described in AOAC First Action Method 2016.15 with minor modifications (addition of detailed integration instructions and a Chinese translation to the 15 laboratories in China). AOAC Official Method 2016.15 Quantification of whey protein content in milk-based infant formula powders SDS-CGE (Sodium Dodecyl Sulfate – Capillary Gel Electrophoresis) (Applicable to determine the whey to casein protein ratio, ranging from 20:80 to 80:20, in bovine milk-based infant formula powders. This method is not applicable to the analysis of hydrolyzed or plant protein-based infant formulas.) Caution: Correct personal and environmental safety standards shall be used while performing this analytical method. Laboratory personnel handling solvents, acids, and reagents should be knowledgeable of their potential hazards. Consult the Material Safety Data Sheets (MSDS) for information on the hazards and take proper precautions. Transfer solvents including β- mercaptoethanol and acids inside efficient fume hoods and extractors. Because of β-mercaptoethanol buildup, perform measurements in a well-vented room. Ideally, install the machine directly in a fume hood. Ensure all glassware is free from chipping and hairline cracks. First Action 2016 Final Action 2017

A. Principle

In SDS-CGE, proteins in infant formula samples are denatured by the anionic surfactant SDS and reduced by β-mercaptoethanol. The SDS-bonded, electrically charged proteins migrate in an electrical field filled with a separation gel and are detected by UV at 220nm. Caseins and whey proteins are separated as two distinct, non-overlapping groups of peaks whose ratio can be established based on integrated areas without the need for a calibration curve. 1.4 was used as the mass-to-area correction