Seed protein contents and nitrogen-to-protein conversion factors for some uncultivated tropical plant seeds

Seed protein contents and nitrogen-to-protein conversion factors were calculated for 13 lesser-known tropical plant seeds based on total nitrogen and the summation of total amino acids. The total protein content, calculated from total amino acid residue, ranged from 4.90 in Diospyros mespiliformis to 32.47 g/100 g fresh weight in Gliricidia sepium. Resulting data gave a mean true conversion factor of 4.97 +/- 1.07 for the leguminoseae. In some seeds, comparisons indicated significant differences between the protein content based on the traditional factor 6.25 and that from amino acid analysis. An average of 22% of the total seed nitrogen appeared to be non-proteinogenic. In general, a conversion factor of 5.5 appears to provide a much more accurate estimate of the seed proteins. It is concluded that the conversion factor based on the total amino acid, rather than the traditional factor 6.25, is more valid for estimating protein contents in terms of nutritional benefits.(C) 2002 Elsevier Science Ltd. All rights reserved.