Preparation and characterization of palm oil in water microemulsion for application in the food industry

Purpose Red palm oil contains both tocopherol (∼30%) and tocotrienol (∼70%) with the latter having better antioxidant potency than the former by a factor of 60 times. The microemulsion is one of the most suitable carriers to protect this vitamin E from environmental stress due to food processing and storage. However, the instability of microemulsion might limit the presentation of vitamin E in the food industry. In the present study, we demonstrated the preparation of microemulsions from different ratios of palm oil and Span 60 to achieve potential carrier formulations for vitamin E delivery. Design/methodology/approach The microemulsions with the different ratios of palm oil and water (o/w) and Span 60 were prepared by using homogenization technique, incubated and observed at 45.0 ± 0.1 °C, room temperature (25 °C ± 0.1) or 8.0 ± 0.1 °C. The microemulsion formed was analyzed by Fourier transforms infrared (FTIR) spectroscopy to observe the molecular composition and the functional groups in the employed oil and emulsifier. Back-scattered dynamic light scattering (DLS) method was employed to determine the stability of microemulsion by measuring the average particle size and polydispersity index (PDI). The zeta potential values of microemulsion were measured by Shape Zeta sizer Nano ZS. The shape and dynamic properties of the microemulsion were observed by Leica optical polarizing microscope (OPM). The creaming, sedimentation, the ratio of aqueous separation and clarification of the microemulsions were evaluated visually whereas the changes in pH were determined using pH meter. Findings The morphological study showed the presence of spherical-shaped particles. The average particle size was found to be the smallest in the presence of 7% Span 60 in the 70/30 (o/w) formulation, and the zeta potential was less than −30 mV for most of the formulations. The most stable pH (the least amount of changes in the pH at room temperature) prevailed for 7% Span 60. Accelerated stability test showed that formulations 30:70 and 50:50 (o/w), in the presence of 5% and 7% Span 60, were the most stable throughout the incubation period. Originality/value The palm oil in water microemulsion in the presence of 7% Span 60 has the potential to be further developed as a delivery system for hydrophobic nutrients such as vitamin E, proteins or peptides and antioxidants in the food and beverage industry.