Comparison of size characterization of barley starch granules determined by electron and optical microscopy, low angle laser light scattering and gravitational field-flow fractionation

Several methods were used for the characterization of starch granules isola ted from barley kernels. A procedure based oil a combination of alkaline di gestion, toluene treatment and filtration over sieves with pore diameters o f 70 and 40 mum was used for isolation and purification of starch granules from kernels. The released starch granules were characterized by various me thods: scanning electron microscopy (SEM) image analysis of optical microsc opy data (IAOM), low angle laser light scattering (LALLS), and gravitationa l field-flow fractionation (GFFF). All methods showed the bimodal size dist ribution of the isolated starch granules, however, they differed in the rat io of large and small starch granules, LALLS and GFFF were also used for de termination of the ratio of large and small starch granules (ratio A/B) iso lated from two malting barley cultivars Kompakt and Akcent. Both techniques determined the higher ratio A/B for the cultivar Akcent. SEM was also used to examine the extent of digestion. The micrographs indicate that a signif icant proportion mainly of small granules are still embedded into residues of endosperm and a more extensive digestion must be performed to release al l starch granules from barley kernels.