Determination of Whey Protein Content in Bovine Milk-Based Infant Formula Finished Products Using Amino Acids Calculation Method: AOAC First Action 2012.08

A method for the calculation of the whey protein fraction was developed for milk-based infant formula products based upon amino acid ratio calculated from asparagine/aspartic acid, alanine, proline, and phenylalanine amino acid data. Historical and literature amino acid data were combined to establish the reference amino acid values used in the validation study. This method has been evaluated for accuracy versus label claim for 12 products, with results from 90 to 107.5% of label claim and an overall average of 98.7%. Repeatability and intermediate precision were determined over 4 different days. Repeatability results were 4.75, 2.06, 4.18, and 2.44% RSD, respectively, with an overall intermediate precision of 3.68% RSD. Since the amino acid profile of infant formula finished products depends on the amino acid profile of ingredients used, the applicability of the method needs to be confirmed for specific types of infant formula, for which data will be gathered. Additional reference material data are being gathered for better estimation of milk and whey reference values, which are based on being normalized to total amino acid content, during the two year AOAC INTERNATIONAL Official Methods of Analysis method approval process.