Nutritive value of globin-amino acid and complementary globin-cereal mixtures

Protein efficiency ratios (PER) were determined using male weanling rats fed diets containing bovine globin alone and with wheat and corn gluten. Simultaneous equations and graphical methods were devised for selecting combinations of globin and cereal proteins to provide optimal and suboptimal profiles of limiting amino acids. Supplementation of the globin with amino acids established isoleucine and methionine as limiting amino acids. Addition of globin, whose amino acid pattern is complementary to that of the cereal proteins, markedly improved the PER values of the proteins. However, growth rates of rats fed various combinations of proteins were not identical, even though PER values differed only slightly. The PER of combined proteins were not predictable from amino acid composition or from correlations between PER and chemical score based on National Research Council (NRC) requirements for essential amino acids. The inability of the optimal mixtures to meet expected nutritional performance clearly indicated that other factors affecting availability of amino acids are implicated. Nevertheless, mutual improvement of two incomplete proteins such as globin and wheat or corn gluten was demonstrated. Addition of globin to widely used diets consisting mainly of corn or wheat can be nutritionally beneficial.