Characteristics of Vanilla Essential Oil Microemulsions with Variations in Stirring Speed and Duration

Abstract

Vanilla fragrance oil has lipophilic properties and high volatility, making it difficult to apply in water-based products without alcohol solvents. This study aimed to determine the effect of stirring speed and duration on the characteristics of vanilla fragrance oil microemulsions and to identify the best treatment combination. A factorial Randomized Block Design was used with two factors: stirring speed (600, 700, and 800 rpm) and stirring duration (6, 7, and 8 minutes). The microemulsion was prepared using a mixture of nonionic surfactants Tween 20, Tween 80, and Span 80 at a ratio of 98:1.5:0.5. Observed variables included transmittance after 24 hours of incubation, transmittance after centrifugation, transmittance at different pH and dilution levels, storage stability, and particle size. The results showed that stirring speed and duration had a highly significant effect (p<0.01) on transmittance values after incubation and centrifugation. The best treatment was obtained at a stirring speed of 600 rpm for 7 minutes, producing transmittance values of 97.3±0.283% after 24 hours of incubation and 96.5±0.424% after centrifugation. pH and dilution tests indicated the highest stability at pH 5.5 with a dilution ratio of 1:99, resulting in a transmittance value of 96.4%. During 8 weeks of storage, transmittance gradually decreased following the linear regression equation y = -8.365x + 94.74 (R² = 99.53%). Particle size analysis showed an average droplet size of 29.9±0.187 nm with a narrow monodisperse distribution. Therefore, stirring at 600 rpm for 7 minutes produced the best vanilla fragrance oil microemulsion characteristics.