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Rheological behaviour of acorn starch dispersions: effects of concentration and temperature

2008; Wiley; Volume: 44; Issue: 3 Linguagem: Inglês

10.1111/j.1365-2621.2008.01760.x

1365-2621

Won‐Woo Kim, Byoungseung Yoo,

Proteins in Food Systems

Summary Rheological properties of acorn starch dispersions at different concentrations (4%, 5%, 6% and 7%) were evaluated under steady and dynamic shear conditions. The flow behaviours of the acorn starch dispersions at different temperatures (25, 40, 55 and 70 °C) were determined from the rheological parameters provided by the power law model. The acorn starch dispersions at 25 °C exhibited high shear‐thinning fluid characteristics ( n = 0.23–0.36). Consistency index (K) and apparent viscosity (η a,100 ) increased with an increase in starch concentration, and were also reduced with increasing temperature. Within the temperature range of 25–70 °C, the η a,100 obeyed the Arrhenius temperature relationship with a high determination coefficient ( R 2 = 0.97–0.99), with activation energies (E a ) ranging between 16.5 and 19.0 kJ mol −1 . Both the power law and exponential type models were employed in order to establish the relationship between concentration and apparent viscosity (η a,100 ) in the temperature range of 25–70 °C. Magnitudes of storage ( G′ ) and loss ( G ″) moduli increased with an increase in the starch concentration and frequency (ω). The magnitudes of G ′ were higher than those of G ″ over most of the frequency range (0.63–62.8 rad s −1 ). The dynamic (η*) and steady shear (η a ) viscosities of acorn starch dispersion at 7% concentration follow the Cox–Merz superposition rule.