RHEOLOGICAL PROPERTIES OF RICE STARCH-MESONA BLUMES GUM MIXTURES

摘要

The effects of Mesona Blumes gum (MBG) at 0, 0.1, 0.35, 0.5, 0.7% (w/w, d.b.) on rheological properties of rice starch pastes (6%, w/w) were investigated. Rice starch-MBG mixtures had pseudoplastic flow behaviors (0.17 ≤ n ≤ 0.24). The effect of temperature (25-65C) on apparent viscosity (η_(50)) was described by Arrhenius equation. Ea values (16.8-22.3 kJ/mol) of rice starch-MBG mixtures varied considerably, indicating a temperature-dependence. Small amplitude oscillatory shear tests at 25C have been modeled by natural logarithm of storage modulus, loss modulus and angular frequency. It was found that rice starch-MBG pastes displayed true gel like behavior. The dynamic (η~*) and steady shear (η_a) viscosities at different MBG concentrations followed the Cox-Merz superposition rule with the application of shift factor (0.0307 ≤ α ≤ 0.114) (R~2 =0.99). Scanning electronic micrographs of these mixtures revealed that the thickness of the network wall increased and the porosity of the network decreased with MBG addition.