The Nutritive Value of the Proteins of Beef Extracted with Different Solvents, and of Egg, Milk and Wheat Germ for the Growing Rat

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Abstract
The nutritive value of beef for growing rats may be reduced markedly by simultaneous dehydration and defatting with ethylene dichloride or propylene under certain conditions. The availability of methionine was decreased significantly by such treatment. Growth was improved by adding methionine or cystine. This reaction is peculiar to beef since the same procedure has been shown to exert no deleterious effect on several other proteins. From the nutritional standpoint, ether, heptane, and trichloroethylene were satisfactory solvents. The importance of testing the influence of technological processes upon the nutritive value of specific foods was emphasized. The regression of daily gain in body weight on intake of nitrogen was significantly greater for egg than for beef, milk, or wheat germ, which were essentially the same. Excellent growth resulted from a diet containing 2.4% of nitrogen from beef, from which the rats ingested on the average 43 mg of methionine and 16 mg of cystine daily. Quantities of other essential amino acids also were estimated. The regressions of nitrogen balance on intake per 100 cm2 of surface area were homogeneous for egg and milk, and significantly higher than for beef or wheat germ. Egg, but not beef, supplemented milk effectively as reflected by nitrogen retention, whereas either egg or beef improved wheat germ.