The amino acid composition of barley grain protein during development and germination

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Abstract
SUMMARY The amino acid composition of barley grain was studied during the maturation of the grain and during germination of the mature grain. Samples of the variety Proctor, grown at two nitrogen levels in each of the years 1969 and 1970, were analysed together with one sample of Sultan grown in 1970. It was found that during maturation the proportions of glutamic acid and proline increased and that the levels of these amino acids were highest in those samples with the highest total protein content. During ripening the proportions of lysine, alanine, aspartic acid, threonine and glycine decreased. On germination the proportions of glutamic acid and proline rapidly decreased whilst aspartic acid, lysine, alanine and glycine increased. The nutritive value of ripe barley grain is limited by its low lysine content. Whilst the germination process increases the level of lysine it is suggested that this does not increase the nutritional value of the grain due to the low level of cystine in the germinated grain.