Structural characterization and rheological properties of a gel-like β-d-glucan from Pholiota nameko.

A crude fraction (SCW) was extracted with cold water from Pholiota nameko and showed mannose (24.1%), galactose (44.9%) and glucose (31%). Purification procedures resulted in a polysaccharide fraction (bG-PN), that showed only glucose. NMR and methylation analyses of bG-PN indicated a β-d-glucan-(1→3)-linked, substituted at O-6 by β-d-Glcp or (1→6)-linked β-d-Glcp side chains. Rheological studies of crude and purified fractions at the same concentration showed similar shear-thinning behavior and gel-like structure which indicates no need to isolate the polymer to achieve some desirable rheological properties. SCW (at 1% and 2%) and bG-PN (at 2%) presented thermal stability during heating and cooling, suggesting that the physical structure of gels (SCW and bG-PN at 2%) and viscoelastic fluid (SCW at 1%) formed were not altered in the tested temperature range. Our results suggest that P. nameko β-d-glucans can be applied in different food preparations as thickener or gelling agents modifying their rheological properties.