The Nutritive Value of Bread Flour Proteins as Affected by Practical Supplementation with Lactalbumin, Nonfat Dry Milk Solids, Soybean Proteins, Wheat Gluten and Lysine

Abstract

The use of “complete protein” as an index of nutritional value is introduced and shown to be superior to that of crude or “total” protein. Experimental results are reported which show a high degree of correlation between the dietary level of complete protein, the growth rate, voluntary food intake, and the protein content of the carcass. Data are presented which confirm that lysine is the limiting amino acid in diets in which wheat flour supplies the major source of protein, and that the rate of growth is not affected by the inclusion of other amino acids furnished by the supplementary protein. A method is proposed for calculating in numerical terms the supplementary value of one or more proteins for a food primarily deficient in a single essential amino acid. The nutritional effects of supplementing wheat flour with lactalbumin, nonfat dry milk solids, soybean proteins, wheat gluten and lysine were investigated. The results accord with the assumption that a well-balanced or “complete protein” contains 5.3 gm of lysine per 16.0 gm of nitrogen. Isonitrogenous diets in which high-protein or low-protein wheat flours supply all the protein, give equal lysine intakes and equal rates of growth.