NITROGEN TO PROTEIN CONVERSION FACTOR FOR 10 CEREALS AND 6 LEGUMES OR OILSEEDS - A REAPPRAISAL OF ITS DEFINITION AND DETERMINATION - VARIATION ACCORDING TO SPECIES AND TO SEED PROTEIN-CONTENT

The main two kinds of usual nitrogen to protein conversion factors (kA and kP) were investigated from the amino acid composition of seed samples with widely varying N content for 10 cereal species and for several legumes and oilseeds. The variations of these factors as a function of seed N content were determined, and their values were compared with the few data from the literature. It was shown that these two factors are the upper and lower limits, respectively, of the total seed N to true protein conversion factor k, which is close to the average of kA and kP. This enabled determination of the factor k with an improved reliability and also comparisons of k values either within a species for distant seed N contents or for a given N content between different species. The conversion factor k varied from 5.1 for N-poor rice grains to 6.0 for N-rich foxtail millet grains. On an average per species, all other species ranged between those two extreme values. They are lower than generally acknowledged until now. © 1990, American Chemical Society. All rights reserved.