| Three hull-less barley genotypes with variable amylose contents were pearled to 10% and roller milled into two major milling fractions, flour and fiber-rich fractions (FRF), in order to determine their composition and compare the distribution and structural variation of non-starch polysaccharides (NSP) originating from their different locations in the barley kernel. Each milling fraction contained various proportions of proteins, starch, ash, and non-starch polysaccharides, mainly beta-glucans, arabinoxylans and arabinogalactans. The pearling-by-products (PBP) were enriched in arabinoxylans, protein and ash and contained small amounts of FRF were considerably enriched in beta-glucans and arabinoxylans. Arabinogalactans were concentrated in the outer portion of the barley kernel. The content and solubility of NSP in various milling fractions was also dependent on the type of barley. The solubility of beta-glucans was higher in PBP than in FRF. The solubility of arabinoxylans was higher in FRF than in PBP. Isolation of water- and alkali-extractable sub-fractions revealed that beta-glucans and arabinoxylans exhibited structural heterogeneity derived from differences in their location within the kernel as well as from barley genotype. Substantial differences in the molecular weight of NSP in different milling fractions were also observed. (Abstract shortened by UMI.)... |
