Assessment of protein quality methodology for infant formulas
Mitchell, G.V.; Jenkins, M.Y.
Journal - Association of Official Analytical Chemists 68(4): 680-683
1985
ISSN/ISBN: 0004-5756 PMID: 4030638 Document Number: 264795
Rat bioassay was used to assess the protein quality of infant formulas and to evaluate the feasibility of using modified casein diets (containing the same source and amount of fat and carbohydrate contributed by the infant formulas) as reference standards. Modification of the casein diet to match the milk-based formulas caused a significant reduction in weekly protein efficiency ratios (PER) and net protein ratios (NPR) at the 3rd and 4th weeks. Modification of the casein diet to stimulate the soya-based formulas had no significant effect on NPR values; PER values were more varied. When PER and NPR values of the dried milk-based formulas were expressed relative to the unmodified reference standard, the relative values were lower than when each matched reference was used. With few exceptions, the relative weekly PER values of the soya-based formulas were similar regardless of the standard used. The relative NPR values of the formulas had a pattern similar to the relative PER values. The data indicate that protein quality evaluation of infant formulas using rat bioassay warrants the use of matched casein reference diets for each type of formula. A biological test with rats was used to assess the protein quality of powdered infant formulae and to evaluate the feasibility of using modified casein diets, containing the same source and level of fat and carbohydrate contributed by the formulae, as reference standards. Modifications of the casein diet to match the milk-based formulae (MF) significantly decreased weekly protein efficiency ratios (PER) and net protein ratios (NPR) at the 3rd and 4th weeks. Modification of the casein diet to stimulate the soya-based formulae (SF) had no significant effect on NPR values; PER values were more varied. When PER and NPR values of the powdered MF were expressed relative to the unmodified reference standard, the relative values were lower than when each matched reference was used. Generally, the relative weekly PER values of the SF were similar regardless of the standard used. The relative NPR values of the formulae had a pattern similar to the relative PER values. The data indicate that protein quality evaluation of infant formulae using rats warrants the use of matched casein reference diets for each type of formula.