AMINO ACID COMPOSITION AND PROTEIN QUALITY OF FIELD PEAS

Abstract

Seed of Century (16 samples) and 17 other lines of field peas (Pisum sativum L.), selected for a wide range of total nitrogen (N), were analyzed for amino acids (AA). Arginine, aspartic acid and glutamic acid were found in greatest amounts, but relatively large amounts of lysine and leucine were also present. A nitrogen-to-protein conversion factor of 5.52 was determined from the AA composition. Variability in AA content within Century samples and among all lines was not large except for arginine, methionine, tryptophan and cystine. Effects of genotype and environment on these AA were equally large. In Century, the concentration of nine AA were significantly correlated with total N. Resulting regression equations reliably predicted the AA composition of Century from total N but were not applicable to other lines of field peas. Apparently, such regressions must be developed independently for each cultivar, i.e. the AA profile is a cultivar characteristic. Peas satisfy adult human requirements for the essential AA except for the sulfur-containing AA, the proportion of which declined with increasing total N. The protein quality was estimated by amino acid score and was equal to 58 for 18 lines of field peas. Threonine and valine were second and third limiting AA, respectively.