Novel Method for Calculating Nitrogen-to-Protein Conversion Factors for Food Protein and Its Application

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The protein content in food is customarily estimated by multiplying the total nitrogen content by the nitrogen-to-protein(N : P) conversion factor, usually set at 6.25. The determined protein content based on this method typically overestimates the true amount of protein in food. This overestimation is mainly due to variations in the amino acid composition and to the presence of nonprotein nitrogen. In this study, we evaluated a practical method of determining more accurately conversion factors for calculating the protein content in food, the principal source of plant and animal protein for humans. We also proposed reliable conversion factors that are calculated by dividing the sum of amino acid residues, based on the amino acid composition, into the total nitrogen content. Although the application of these novel N : P factors for nutritional estimation has not yet been put into practical use, it is able to calculate an acceptable approximation for the actual protein content in food.