Improvement the amino acids determination method to establish the procedure for determining nutritional protein in food sample
Abstract
Analysis of amino acid composition is the only way to evaluate the nutritional value of food. The analytical procedure is often complicated and time-consuming. Improving the analysis is, therefore, necessary to control the use of nonprotein nitrogenous constituens in food. The main contributions of the study on the analysis of 25 protein AAs are: (i) The use of borate buffer which facilitated the dansylation of AAs; (ii) The improvement of liquid chromatographic separation using ion-paring technique in reversed-phase mode at low pH with “bidentate bonding” column. Not only the resolutions of the AAs were improved but the retention factors of aspartic acid (Asp), glutamic acid (Glu) and cysteic acid (Cys) were also enhanced; (iii) The discovery of a medium consisting of 5 % thioglycolic acid (TGA) and 0,2 % phenol in H2SO4 3M for the hydrolysis of BSA, a model protein. With this medium the fragile side chains can be protected. The developed hydrolysis procedure was very simple, efficient and fast (only 4 hours).