Relationships between structural features, molecular weight and rheological properties of cereal β-D-glucans

Although cereal β-D-glucans exhibit similar C13-NMR spectra, their structural features are different from each other as evident by the ratios of tri- and tetrasaccharides released from lichenase hydrolysis (4, 3, and 2 for wheat, barley and oat p-D-glucans, respectively). This chapter demonstrates the correlation between the structural features, molecular weight, and some physical properties including solubility of freeze-dried samples and gel forming aptitude. Rheologically, cereal β-D-glucans behave similarly to random coil polysaccharides; however, some β-D-glucans can form gels under certain conditions, which is not observed for other random-coil polysaccharides including galactomannans. The gelling ability and insolubility of freeze-dried cereal β-D-glucans followed the order of wheat > barley > oat; this trend corresponds with the ratio of tri- and tetrasaccharides of cereal β-D-glucans. In addition to the structural features, molecular weight also plays an important role in the conformation of cereal β-D-glucans in aqueous systems. The results indicate that lower molecular weight β-D-glucan is easier to form a gel than larger molecules.