Abstract
Summary
1. A microbiological method to assess the biological value of proteins is described. It implies the digestion of proteins with pancreatin and subsequent testing of the growth-promoting activity of the hydrolysate for S. faecalis, in a medium devoid of the 10 essential amino acids. The nutritive value of the protein digest is determined in a single assay by the amino acid liberated in a limiting concentration. 2. The results obtained with casein, egg albumin, gelatin, gluten, and zein are presented and their agreement with the biological values obtained by the rat growth method is suggested. 3. The growth promoting activity (biological valued) of casein and egg albumin is high and about equal; gelatin and gluten, in comparison, are much less active, 29 and 15%, respectively, and zein still less (2%). 4. At the limited growth level, casein is deficient in: lysine, arginine, isoleucine, and threonine. Egg albumin under comparable conditions is limited in lysine, arginine, histidine, threonine, isoleucine, leucine, and valine. Gelatin is low in tryptophane, isoleucine, leucine, methionine, and threonine. Gluten and zein are short in lysine. 5. The suitability of the method described for studying imbalances of amino acids is proposed.
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