A method for the calculation of whey protein fraction in milk-based formula products was developed and validated by a group of researchers from Abbott Nutrition, Covance Laboratories and AOAC International. The method is based on calculating the ratio of (Asx + Ala)/(Pro+Phe) determined from the amino acid profile of the hydrolyzed sample.
The method was approved as AOAC Official First Action Method 2012.07 and is appropriate for accessing compliance with whey content requirements of GB 10765-2010 (National Food Safety Standard Infant Formula)*. It is applicable to finished products containing both intact and partially hydrolyzed whey proteins.
According to this method, the Amino Acid Profile of hydrolyzed samples is determined using cation-exchange chromatography with post-column derivatization and UV/Vis detection. The researchers used Pickering Laboratories post-column derivatization system, our patented Trione Ninhydrin reagent and Pickering Sodium analytical column and buffers.
The method performance was evaluated using non-fat dry milk and products with whey levels from 32% to 63%, including NIST Infant Formula Standard Reference Material. The repeatability ranged between 0.3 and 2.5 %, while intermediate precision were between 2.6 and 3.4%. Average recoveries ranged from 97 to 100%.
The unmatched accuracy and precision of amino acid analysis by HPLC with post-column derivatization allowed the researches to develop a robust mathematical model for calculating whey protein fraction that can be successfully applied to a wide range of products. This proved once again that post-column derivatization analysis of amino acids is still a method of choice for laboratories that require highly accurate results.
Pickering Laboratories offers a total solution for amino acids analysis, including post-column derivatization systems, reagents, columns, buffers and standards.
The reference to the published study is below. The First Action Official Method 2012.07 can also be found online at http://www.eoma.aoac.org/.
Calculation of Whey Protein Fraction in Milk-Based Infant Formula: First Action 2012.07
Authors: Wesley Jacobs, Paul Johns, Phillip Haselberger, Joseph J. Thompson, Darryl Sullivan, Steve Baugh.
Source: Journal of AOAC International, Volume 96, No. 3, 2013, pp. 502-507
(*) this is a Chinese Standard