Structure analysis of β-glucan in barley and effects of wheat β-glucanase

In this study, β-glucan in samples of sifted flour from six barley varieties was sequentially extracted with water and NaOH obtaining three fractions: water-extractable (WE), NaOH- extractable (NaE) and residual (Res). β-Glucan isolates were incubated with lichenase and oligomers released were analysed with high performance anion exchange chromatography coupled with pulsed amperometric detection (HPAEC-PAD). A higher ratio of 3-O-β-cellobiosyl-D-glucose (DP3) to 3-O-β-cellotriosyl-D-glucose (DP4) is reported in WE, NaE and Res fractions in variety SLU 7 (shrunken endosperm) compared to the other varieties, suggesting a more packed β-glucan structure. Water-extractable and water-unextractable β-glucan fractions were incubated with wheat extract and effects of wheat β-glucanase on the structure was assessed after lichenase digestion and analysis with HPAEC-PAD. Findings suggest that wheat β-glucanase manifests a selective hydrolysis towards β-glucan with lower DP3/DP4 ratio and that β-glucan of SLU 7 is composed of a population with higher DP3/DP4 ratio and hence with a more tighten structure which may be more resistant to enzymic action. Overall, the results obtained are of interest to characterise barleys differing in starch and dietary fibre composition, specifically shrunken endosperm barley SLU 7 in the perspective of its inclusion in the production of β-glucan enriched foods.