Net Protein and Growth-Promoting Values of Three Different Types of Yeast Prepared under Identical Conditions

Abstract

The nutritive value of the proteins of three different types of yeasts prepared under identical conditions was evaluated by means of the nitrogen balance and growth-promoting methods. The Saccharomyces cerevisiae, Bakers' No. 51 and Brewers' No. 52, and Torula utilis No. 1084 were found, respectively, to be 80.7, 79.9, and 84.8% digestible; to possess biological values of 58.9, 58.4, and 31.8; to have net protein values of 22.7, 22.2, and 14.9; and to possess a proteine fficiency of 1.4, 1.7, and 0.9. With the exception of the coefficient of digestibility, the nutritive coefficients of S. cerevisiae strains were generally much higher than those of the Torula. The protein of Torula utilis No. 1084, when supplemented by 0.5% methionine, gave the following nutritive coefficients: digestibility, 90.2; biological value, 88.3; net protein value, 44.1; and protein efficiency, 2.0. The two strains of S. cerevisiae, Bakers' No. 51 and Brewers' No. 52, had similar nutritive coefficients with the exception of that for protein efficiency, which was higher in the case of strain 52.