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Steady and Dynamic Shear Rheology of Rice Starch‐Galactomannan Mixtures
Author(s) -
Yoo Dongryel,
Kim Chion,
Yoo Byoungseung
Publication year - 2005
Publication title -
starch ‐ stärke
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.62
H-Index - 82
eISSN - 1521-379X
pISSN - 0038-9056
DOI - 10.1002/star.200400390
Subject(s) - starch , rheology , locust bean gum , galactomannan , guar gum , rheometry , arrhenius equation , chemistry , dynamic modulus , shear thinning , apparent viscosity , dynamic mechanical analysis , materials science , food science , polysaccharide , activation energy , biochemistry , composite material , xanthan gum , organic chemistry , polymer
Rheological properties of rice starch‐galactomannan mixtures (5%, w/w) at different concentrations (0, 0.2, 0.4, 0.6 and 0.8%, w/w) of guar gum and locust bean gum (LBG) were investigated in steady and dynamic shear. Rice starch‐galactomannan mixtures showed high shear‐thinning flow behaviors with high Casson yield stress. Consistency index ( K ), apparent viscosity (η a,100 ) and yield stress (σ oc ) increased with the increase in gum concentration. Over the temperature range of 20–65°C, the effect of temperature on apparent viscosity (η a,100 ) was described by the Arrhenius equation. The activation energy values ( E a = 4.82–9.48 kJ/mol) of rice starch‐galactomannan mixtures (0.2–0.8% gum concentration) were much lower than that ( E a = 12.8 kJ/mol) of rice starch dispersion with no added gum. E a values of rice starch‐LBG mixtures were lower in comparison to rice starch‐guar gum mixtures. Storage ( G ′) and loss ( G ′′) moduli of rice starch‐galactomannan mixtures increased with the increase in frequency (ω), while complex viscosity (η*) decreased. The magnitudes of G ′ and G ′′ increased with the increase in gum concentration. Dynamic rheological data of ln ( G ′, G ′′) versus ln frequency (ω) of rice starch‐galactomannan mixtures have positive slopes with G ′ greater than G ′′ over most of the frequency range, indicating that their dynamic rheological behavior seems to be a weak gel‐like behavior.