Development and optimization of a microwave-assisted protein hydrolysis method to permit amino acid profiling of cultivated and wild wheats and to relate the amino acid to grain mineral concentrations

Official URL: http://192.168.1.20/record=b1301396 (Table of Contents)

Wholegrain flour from durum wheat (T.durum, cv. Balcali-2000) was subjected to amino acid analysis following microwave-assisted acid hydrolysis. To optimize this new method, a range of sample masses (100-500 mg), incubation temperatures (130-170[centigrade degree]) and time intervals (1- 4h) were assessed. Overall, the greatest recovery of amino acids was obtained when 200 mg of wheat flour sample was hydrolyzed at 150[centigrade degree] for 3 h. The developed microwave hydrolysis method was confirmed to yield comparable findings with classic reflux methods. Integration of all amino acid signals corresponded to 85 % of the total protein content calculated by total N. The highest signal reflected the combined contributions of glutamic acid and glutamine, in accord with previous findings. Also as expected, proline was found to rank in second place. It follows to reason that an optimized microwave-assisted hydrolysis method may describe a rapid means to compare the constitution of different genotypes of wheats and may further show merit and general applicability towards the rapid analysis of commercially important crops and their end-products. In all wheat species and genotypes Glu was the most abundant amino acid, followed by Pro, whereas Met sln, Lys and Thr were the most limited. The quantities and ratios of individual amino acids were consistent with the literature data and the quantitative order of major and minor amino acids did not change in genotypes or species. However, amino acids exhibited significantly high variations among genotypes and species which can be exploited to enhance specific and/or total amino acids (i.e. protein) in high yielding cultivated wheats through selection, breeding and targeted molecular approaches. Although the existence of significant associations between a few amino acids and mineral nutrients, it was not possible to define or explain a co-transport or co-accumulation mechanism. Future research should focus on the phloem transport and mobility of metal binding proteins and organic ligands, rather than individual amino acids. A major finding of this study was the augmentation of correlations (among amino acids, nutrients and amino acids with nutrients) upon prescreening for contrasting grain N (or protein) concentration. Advancements in increasing the grain protein content of wheat can significantly contribute to enrichment of grains with almost all mineral nutrients except K and Ca.