RHEOLOGICAL PROPERTIES OF RICE STARCH-MESONA BLUMES GUM MIXTURES

Abstract

ABSTRACT 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 (η50) 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 (ηa) viscosities at different MBG concentrations followed the Cox–Merz superposition rule with the application of shift factor (0.0307 ≤ α ≤ 0.114) (R2 = 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. PRACTICAL APPLICATIONS Rice starch and Mesona Blumes gum mixtures might be used as a fat-replacer, meat binder or jelly food. Therefore, it is necessary to investigate the rheological properties of such a mixture. Through steady and dynamic shear rheological experiments, the regularity of MBG and rice starch interaction will be used to guide our application. Also, it might be predicted by Cox–Merz superposition rule to show what would be the optimal ratio between these two macromolecules. Therefore, the microstructure of these macromolecular mixtures was investigated by scanning electronic micrographs to further understand their rheological properties.