Improved Performance of the Reference Casein Control Group in AOAC Official Method^SM 960.48 (Protein Efficiency Ratio, Rat Bioassay) for Determining the Biological Quality of Protein in Infant Formula.

This article focuses on improving the performance of the reference casein control group in AOAC Official MethodSM 960.48, a protein efficiency ratio (PER) rat bioassay used to determine the biological quality of protein in infant formulas. Two studies demonstrated that using the method's specified mineral mixture, which contains a relatively high level of inorganic sulfate, enhances growth and PER outcomes in control rats fed low-protein casein diets, compared to control diets matched only to infant formula mineral content. The addition of cystine to the control diet increased PER but reduced the assay's sensitivity, suggesting it is not an appropriate modification under standard conditions. The findings emphasize the importance of adhering to AOAC Method 960.48 and FDA recommendations to ensure valid and consistent assessment of protein quality in infant formulas.