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

BACKGROUND

AOAC Official MethodSM960.48 is the official method for ensuring the biological quality of protein in infant formulas after adjusting for differences in N, fat, ash, moisture, crude fiber, fat content, and carbohydrate type.

OBJECTIVE

To improve the performance of the control diet group.

METHOD: The control diet in Study 1 was matched to the infant formula test diet. Both control diets in Study 2 used the AOAC mineral mixture; one had added cystine.

RESULTS

In Study 1, deficient growth in control rats led to poor PER results. In Study 2, growth was adequate but cystine addition reduced meaningful differences between casein and infant formula protein.

CONCLUSIONS

Sulfate salts in the method's mineral mixture may substitute in part for the deficient organic sulfur content in casein.

HIGHLIGHTS: The findings confirm the need to follow the AOAC Method 960.48 and FDA recommendations, and to make other changes only if, after evaluation, nonprotein differences could affect growth.