Formulation and stability of water-in-virgin coconut oil microemulsion using ternary food grade nonionic surfactants

This study was intended to obtain formulation of water-in-virgin coconut oil (w/o) microemulsions and to determine its stability. The stable w/o microemulsions were prepared based on the hydrophilic lipophilic balance (HLB) concept by using ternary nonionic surfactants combination having low, medium, and high HLB values. Microemulsions were formulated with ternary surfactants mixture consisting of Span 80, Span 20 and Tween 20 to achieve predetermined HLB values of 6.0, 6.5, 7.0, 7.5, and 8.0. These values were subsequently used to determine the proportion of water, surfactant, and oil to obtain microemulsions. These microemulsions were subjected to stability tests which include centrifugation, heating treatment, and storage at room temperature. The results indicated that a clear w/o microemulsion was successfully formulated containing 75% of oils portion. It required surfactant and water ratio of 4.5:1 or higher. When the microemulsions were formulated to contain 77.78% oils, the surfactant and water ratio is at least 5.5:1 or higher. These microemulsions remained stable during storage, even after centrifugation, but they were not stable when subjected to heating at 70°C or higher. This study confirmed that water-in-virgin coconut oil microemulsion is obtainable and suitable for carrying hydrophilic bioactive compound in food application.