Nitrogen-to-protein conversion factors for some common edible mushrooms

Mushrooms (13) common to Japan were analyzed for total nitrogen (TN), amino acid nitrogen (AAN), amide-N and nonprotein nitrogen. The distribution of protein nitrogen averaged 67% to TN. Averaged nitrogen-to-protein conversion (N:P) factor was 5.99. Application of the factor for estimation of protein content resulted in a considerable difference from amino acid residue (AAres) levels, due to the high level of nonprotein nitrogen. A net N:P factor, defined as the proportion of AAN to TN, was proposed. The averaged value of 3.99 was derived from analytical TN and AAN data of mushrooms. Calculated protein values using this factor were in good agreement with AAres.