Dynamic viscoelastic behavior of triple helical Lentinan in water: Effect of temperature

This study deals with the dynamic viscoelastic property for Lentinan fractions with different molecular weight in water under different constant temperatures and polysaccharide concentrations. The results revealed that a transition exists between a sol-like and a weak gel behavior for the Lentinan/water system. The gel point, Tgel, was determined from the point of intersection in tan δ vs. temperature (T) for different constant frequencies, indicating the validity of Winter–Chambon criteria. The Tgel decreased with decreasing polymer concentration and molecular weight. Moreover, the value of exponent n at the gel point decreased with increasing polymer concentration but exhibited an independence of molecular weight, indicating that the gels of Lentinan had similar fractal structure. The dynamic strain sweep measurements proved that the gelation of Lentinan in water is induced by the extremely entangled and stiff triple helices forming continuous network, and the Lentinan gel is structurally more like a solution that is unable to flow within a timescale of usual observation. The heating–cooling process proved that the sol–gel transition of Lentinan in water was thermally reversible.