Nutritional Value of Proteins of Oriental Soybean Foods

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Abstract
The protein quality of oriental foods of soybean origin has been determined by the net protein utilization (NPU) method at a 10% level of protein in the diet. This method calls for the determination of whole body nitrogen by the Kjeldahl method and its calculation from body moisture on 77 male and female weanling rats fed varying quantity and quality of proteins for 10 days. The correlation coefficient for the body nitrogen values obtained by the 2 procedures was 0.947. This high correlation permitted the computation of whole body nitrogen from body water in subsequent experiments. The proximate compositions of the soybean products were in agreement with those in previous reports. The generous amount of protein in edamame, tofu, and natto is confirmed. The NPU of the control proteins, powdered whole egg and crude casein, was 90.4 and 67.3, respectively, which corresponded to values reported by Miller and Bender using the same method. The NPU values obtained for the soybean products were 72.2, 65.0, 56.0, 44.4, and 35.6 for edamame, tofu, soybean sprouts, natto, and mung bean sprouts, respectively. Edamame and tofu, being both of good quantity and quality in protein, appeared to be dependable vegetable protein sources.