The influence of stirring speed and type of oil on the performance of pregelatinized waxy rice starch emulsifier in stabilizing oil-in-water emulsions

The performance of pregelatinized waxy rice starch (PWRS) as an emulsifier in coconut oil and hexadecane emulsions was examined. Emulsification was carried out at various stirring speeds (Ultra-Turrax at 8000, 11,000, and 15,000 rpm with an oil content of 10%). Two treatments were used to test the stability of the emulsions: under a static condition for two weeks and under thermal treatment using differential scanning calorimetry (DSC) at −30 to 50 °C for three cycles. The changes in the structure of the PWRS caused by high shear stress at the stirring speed of 15,000 rpm induced creaming in all the emulsions. The ability of the PWRS to protect the oil droplets was influenced by the type of oil and environmental conditions. PWRS was better adsorbed on coconut oil than on hexadecane as signified by the values for relative apparent viscosity and yield stress, what was observed in photomicrographs, and the changes in 1D H NMR intensity at different PWRS concentrations.