Structural characterization and rheological properties of an alkali-extracted β-glucan from Hypsizygus marmoreus

A homogeneous β-glucan (JHMP-70) was obtained from Hypsizygus marmoreus by alkali extraction and ethanol precipitation, and had an apparent molecular weight of 394 kDa. Its fine structure was investigated by FT-IR, methylation combined with GC-MS and 1D and 2D NMR analysis. Results indicated JHMP-70 was a branched β-(1 → 6)-glucan substituted at O-3 by the non-reducing β-Glcp and/or β-(1 → 3)-linked β-Glcp side chains at a ratio of 1:1. SEM observation revealed that there were micro-spherical shapes intertwined with randomly distributed fibrous filaments. Rheological measurements showed that its flow behavior was highly dependent on the concentration. Newtonian behavior was evident at low concentration, whereas pseudoplastic behavior was observed at high concentration. Besides, the addition of salt ions (Na + or Ca2+) significantly decreased the apparent viscosity of JHMP-70 solution. The low viscosity of JHMP-70 was probably attributed to its structural features, including main chain structure, branching degree and side chain length. This work can provide a basis theory to expand the application of the polysaccharides from H. marmoreus in food industry, because their lower viscosity and superior fluidity are desired in beverage products to impart stability against phase separation without compromising other sensorial properties.