Characterization and chemical stability evaluation of β-carotene microemulsions prepared by spontaneous emulsification method using VCO and palm oil as oil phase

β-carotene is one of the major carotenoids in the human diet which shows pro-vitamin A activity, and is associated with prevention of cardiovascular diseases, cancer, and immune system enhancer. However, the poor water-solubility, high melting point, and chemical instability of carotenoids is currently a challenge to their application in the food sector. In this research, the characteristics of β-carotene microemulsions (0.025%, 0.05% wt) prepared with ternary food grade surfactants (Span 80, Span 40, Tween 80) and VCO (virgin coconut oil) or palm oil as oil phase, using spontaneous emulsification method were evaluated. Chemical stability of β-carotene loaded microemulsions during storage was also examined. The result showed that β-carotene microemulsions prepared using either VCO or palm oil had viscosity, specific gravity, refractive index and pH values which were not significantly different. The mean particle diameters (z-average) of the β-carotene microemulsions ranged from 20 – 23 nm and the size distributions were monomodal with a narrow particle size range from 10 – 50 nm. The β-carotene microemulsions showed significantly different zeta potential, i.e.: -14.4 ± 0.8mV (VCO, 0.025 %wt), -10.6 ± 0.3 mV (VCO, 0.05 %wt), -24.6 ± 1.0 mV (palm oil, 0.025 %wt) and -16.6 ± 0.9 mV (palm oil, 0.05 %wt). The β-carotene degradation during storage was slower in microemulsions with palm oil as an oil phase than that of VCO as an oil phase. These results have important consequences for the design and utilization of microemulsions as delivery systems to encapsulate and stabilize β-carotene for food or pharmaceutical applications.