The Importance of Commercial Processing for the Protein Value of Food Products

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Abstract
Using the nitrogen balance method of assessing the protein values of foods with growing rats, it has been shown that the digestibility and biological value of the proteins of the soybean can be increased by heat processing, and that the explosion process, if not carried to extremes, can raise the digestibility of the protein by 11 percentage units and the biological value by 16 percentage units. In the autoclaving of soybeans, the improvement in the nutritive value of the protein seems to be entirely referable to an improvement in the availability of the contained cystine. In the commercial oil extraction of other oil-bearing seeds than the legumes, the drastic heat treatments commonly employed may be expected to exert a destructive action upon the heat labile nutrients, including protein. Applied to the coconut, a solvent extraction procedure carried out at temperatures that never exceed 75°C., yields a product whose protein is 86% digestible and possesses a biological value of 71, considerably higher than that of a product tested earlier that had been prepared by the usual drastic methods. The protein of sunflower seed meal, prepared by the same process, was found to be 94.3% digestible and to possess a biological value of 64:5. Due to its high initial content of protein, 55.4% on the dry basis, the “net protein” content of this food was higher than that of any of the other foods tested, i.e., 33.7%. The significance of a mild, gentle process of extracting oil from nonleguminous oil-bearing seeds in the preparation of protein foods for human consumption seems worthy of further study.