Rheology of The Glutinous Rice Flour, Coconut Milk, and Palm Sugar Mixed System in A Traditional Food Dodol Ulame

Abstract

Triple mixed of glutinous rice flour, coconut milk, and palm sugar paste with ratio of 1.0:2.5:0.5, 1.0:2.0:1.0, 1.0:1.5:1.5, 1.0:1.0:2.0, 1.0:0.5:2.5 were studied using rapid visco-analyzer (RVA), rheometer, and polarized light microscope to investigate its pasting properties, flow behavior index, dynamic rheology, and microstructure respectively. The power-law and Herschel-Bulkley models were used to evaluate its steady rheological properties. The RVA profile shows low viscosity profile and low breakdown viscosity for all ratio of dodol ulame paste. The lowest breakdown viscosity occurred at the ratio of 1.0:2.5:0. Meanwhile, the highest setback viscosity occurs at the ratio of 1.0:0.5:2.5. Indicating the highest riqidity due to high sugar content. The apparent viscosity decreased with increasing shear rate for all triple mixed exhibited a typical shear-thinning behaviour (n<1) of the system. Increasing the proportion of coconut milk decreased the consistency coefficient, k, and increased the flow behaviour index, n of the system. The dynamic rheology resulted in the higher G” value over the entire frequency. Maltese crosses disappeared at 90 °C for the ratio of system 1.0:0.5:2.5 and 1.0:1.0:2.0 and 80 °C for the ratio of system 1.0:1.0:2.0, 1.0:1.5:1.5 and 1.0:1.0:2.0. The study suggests that coconut milk and palm sugar had an important role on the rheology of dodol ulame paste, consequently it affects the gelatinization, viscosity, and gel-like behaviour of the glutinous rice flour, coconut milk, and palm sugar mixed system. Further study on the preference and nano structure is undertaken to reveal its possibility to produce better quality dodol ulame.