A Comparison of the Nutritive Value of Egg Proteins and Their Amino Acid Content

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Abstract
The proteins of whole egg, whole egg white, and yolk were prepared and analyzed for cystine, methionine, phenylalanine, tryptophane, threonine, arginine, histidine, lysine, sulfur, and nitrogen. These proteins were incorporated into diets at a 10% level and fed to young rats. The protein efficiency (ratio gain in wt./g. of protein ingested) was detd. after a 2 wk. feeding period. Commercial prepns. of whole egg and whole white protein were similarly analyzed and their PE ratio detd. The PE ratio of the whole white protein was higher than that of either the whole egg or the yolk proteins. The PE ratio of the commercial whole white protein was almost as high as that of the lab. prepared sample. The amino acid content of all the whole egg proteins were quite similar with the exception of the cystine content of the commercial samples which was lower than that of the lab. samples. When the commercial whole egg protein was re-enforced with 0.25% cystine the PE ratio was not improved. Other factors in addition to the amino acid content apparently play a role in the biologic value of proteins.