Characterization and modeling of the A-and B-granule starches of wheat,triticale,and barley

摘要

Wheat,triticale,and barley starches have large,disc-shaped A-granules and small,spherical B-granules.In this study,A-and B-gran-ules of these three starches were separated,and their structures and properties were analyzed.Absolute amylose contents of wheat,triticale,and barley A-granules were 30.9,28.2,and 28.1,respectively,and that of the B-granules were 25.5,19.7,and 23.0,respectively.High-performance anion-exchange chromatography,equipped with an on-line amyloglucosidase reactor and a pulsed amperometric detector(HPAEC-ENZ-PAD),of debranched amylopectins showed that the A-granules had more B_2 chains and lesser short chains(A and B_1 chains)than did the B-granule counterparts.Structure models of the amylopectins of the A-and B-granule starches were proposed,and the relationships between the structures of amylopectin and the shapes of starch granules were discussed.The B-granules displayed higher peak gelatinization temperatures and broader gelatinization temperature ranges than did the A-granules.The retrogradation rates of the B-granules after being stored at 4 deg C for 7 days were less than that of the A-granules.The B-granules had higher pasting temperatures,less peak,breakdown,and setback viscosity than did the A-granule counterparts.The pasting properties of reconstitute wheat starch consisting of different proportions of the A-and the B-granules showed that the chemical composition and structure of the starch,instead of the size of the starch granules,controlled the pasting properties of the starch.The differences in the structure of the A-and B-granules suggested that biosynthesis of the two granules differed.