Effect of Heating on the Viscosity and Rheology of Grewia mollis, Bombax ceiba and their Binary Mixture
This study determined the effect of concentration and prolonged heating on the rheological properties of gums from Grewia mollis, Bombax ceiba and their binary mixtures. After extraction, the gums were divided into four batches each. The binary mixture was obtained by triturating Grewia mollis and Bombax ceiba gum in a ratio of 1:1. The first batch was made up of 0.5 % w/w, 1.0 % w/w, 1.5 % w/w and 2.0 % w/w and the viscosity and flow rate of each percentage concentration was determined. The remaining three batches were made from grewia and bombax gums boiled in 0.1 N HCl for 1, 2 and 3 h, after which it was allowed to cool and precipitated out with 95% ethanol, dried at room temperature for 24 h then in hot air oven at 60°C for 1 h. Solutions of individual and binary mixtures were made as the first batch after which their viscosities and flow rates were determined. Heating of the gums was shown to reduce viscosity of the gums, but this was more significant at lower concentrations. Grewia gum was more resistant to viscosity change due to heating than bombax gum and their binary mixture did not significantly affect this increase. Heating of the gums led to decreased viscosity, while flow rate increased.
Keywords: Bombax ceiba, Grewia mollis, binary mixture, heating, viscosity.