Steady Shear Rheological Properties of Native and Hydrothermally Modified Persian Acorn (Quercus brantii Lindle.) Starches

Abstract

The steady shear rheological properties of native and hydrothermally modified Persian acorn starches at different concentrations (1, 2, and 3%) and temperatures (25, 40, 55, and 70 °C) were assessed. The rheological data of starch dispersions were fitted to the power law (R2 = 0.769–0.980) and Casson models (R2 = 0.904–0.994). According to the power law model, all native and hydrothermally modified starches presented shear‐thinning behavior with the flow behavior index between 0.697 and 0.933. The consistency coefficient (k) and apparent viscosity (ηa,100) of starches were in the range of 3.157–246.167 mPa sn and 2.212–74.443 mPa s, respectively. Based on the Casson model, the plastic viscosity (ηc) and yield stress (τ0c) of starches were in the range of 1.977–41.167 mPa s and 0.333–506.667 mPa, respectively. All rheological parameters, except for the flow behavior index, increased with increasing in concentration, and decreased with temperature. The temperature dependency of all the starches was well described by the Arrhenius model (R2 = 0.837–0.999). The activation energy (Ea) values were in the range of 4.47–12.96 kJ mol−1. The concentration dependency of all the starches in the temperature range of 25–70 °C was well fitted to the power law (R2 = 0.919–0.998) and exponential (R2 = 0.970–0.999) models. Generally, the rheological parameters such as k, ηa,100, ηc, and τ0c of native starch were maximum and those of annealing (ANN) starch were between those of native and heat‐moisture‐treatment (HMT) starches. These properties for dually modified starches were between those of single ones, showing that the second treatment could negate the effects of the first one.