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)-beta-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 beta-glucans formed elastic gels after 4 days at 4degreesC whereas larger molecular weight beta-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 +/- 2degreesC. Partial hydrolysates produced with cellulase, which was shown to preferentially cleave regions of the molecule with longer contiguous beta-(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 beta-(1 --> 4) glycosidic 3-o-substituted glucose links. This suggests that beta-(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. Crown Copyright (C) 2003 Published by Elsevier Ltd. All rights reserved.