Oscillatory and steady shear rheology of gellan/dextran blends

Abstract

Oscillatory and steady shear rheology of gellan (G) and dextran (D) solution individually, and in blends (G/D ratio 1:1, 1:2, and 1:3 w/v) with a total hydrocolloid concentration of 3 % (w/v) were studied at 25 °C. Individually, 1.5 % dextran and 1.5 % gellan in solution exhibited Newtonian and non-Newtonian behavior, respectively. A blend of equal proportion of dextran and gellan (G/D = 1:1) exhibits a distinct gel point (G′ = G″), and further addition of dextran in the blend (G/D = 1:2 and 1:3) resulted predominating liquid-like (G″ > G′) behavior. A plot of G′ vs G″ distinctly showed the gradual transition of the blend. Shear stress (τ)-shear rate (γ⋅$$ \overset{\cdot }{\gamma } $$) data fitted well the Herschel–Bulkley model. The G/D blend exhibited shear thinning behavior with flow behavior index less than unity. The Cox–Merz rule did not fit well for the complex shear viscosity (η*) and apparent viscosity (η) of the blend.