Effects of Carnauba Wax Addition on Physical States of Palm Kernel Oil-in-Water Emulsions.

The effects of carnauba wax addition on the physical state of palm kernel oil-in-water emulsions were investigated, The oil-in-water emulsion (40 wt% oil +60 wt% aqueous phase) kept the liquid state at 25 degrees C irrespective of the presence or absence of carnauba wax in the oil phase. The emulsion containing the wax transformed from the liquid state to the solid state by shearing after storage for 20h at 4 degrees C, although the liquid-solid transition was not observed for the emulsion not containing the wax upon the same treatment. The viscoelasticity of the solid emulsions was demonstrated by small-deformation mechanical testing, Analysis of flow behavior of the emulsions showed that the change in physical properties of the emulsion containing the wax at 4 degrees C was caused by the shearing at a low shear rate, around 50 s(-1)-100 s(-1). According to the transition from the liquid state to the solid state of the emulsion containing the wax, the aggregation of oil droplets was found to occur to a large extent, The results of differential scanning calorimetry and surface pressure-surface area isotherms suggested that triglyceride molecules of palm kernel oil were more oriented at the oil-water interfaces in the emulsions after the wax addition, Based on these results, it is thought that carnauba wax is important in destabilization of palm kernel oil-in-water emulsions by modifying the physical state of the oil triglyceride molecules at the interfaces.