Structural characterization and rheological properties of β-D-glucan from hull-less barley (Hordeum vulgare L. var. nudum Hook. f.)

A high purity of beta-D-glucan (80.8%) from hull-less barley (Hordeum vulgare L. var. nudum Hook. f.) (HBBG) was isolated by alkali extraction and multi -precipitation with ethanol. The molecular weight (Mw) of HBBG was determined as 571.4 kDa with a broad distribution (Mw/Mn = 1.6) by using HPSEC. According to methylation and GC-MS analysis, HBBG was identified to be composed of (1 -> 4)- and (1 -> 3)-glucopyranosyl (Glcp) residues with a ratio of (3.19 +/- 0.01). The MALDI-TOF MS and NMR spectroscopy were further conducted to analyze the enzyme hydrolysate released by lichenase digestion on HBBG. The results suggested that HBBG possessed a typical chemical structure of cereal 13-o-glucans, namely linear homopolysaccharides formed by beta-D-Glcp units via (1 -> 4)-linkages and occasionally single (1 -> 3)-linkage. The trisaccharide and tetrasaccharide of HBBG accounted for 66.6% of total cellulosyl units, accompanying with a ratio of cellotriosyl to cellotetraosyl units = 1.0, which were significant different from those reported for the other cereal beta-glucans. Rheological property analysis revealed that HBBG showed a shear-thinning behavior and thermal resilience during heating cooling process.