Structural characteristics and rheological properties of partially hydrolyzed oat β-glucan: the effects of molecular weight and hydrolysis method

Partial hydrolysates of (1→3)(1→4)-β-d-glucan from oats were produced by three hydrolysis methods: acid, cellulase or lichenase. The molecular weights ranged from 31 000 to 237 000 g/mol. Six percent solutions of small molecular weight β-glucans formed elastic gels after 4 days at 4 °C whereas larger molecular weight β-glucans remained viscous liquids after 7 days. The melting temperature of the gels increased as they aged and the peak heat flow temperature, measured by differential scanning calorimetry, was 62±2 °C. Partial hydrolysates produced with cellulase, which was shown to preferentially cleave regions of the molecule with longer contiguous β-(1→4)-linked d-glucopyranosyl units, tended to produce more elastic gels with stronger junction zones than partial hydrolysates produced with lichenase which cleaves the β-(1→4) glycosidic 3-o-substituted glucose links. This suggests that β-(1→3)-linked cellotriose sections of the polymer are probably the segments which form the junction zones in the gel network rather than cellulose-like segments.