Optimisation of Cinnamaldehyde-in-water Nanoemulsion Formulation using Central Composite Rotatable Design

Thirteen formulations of cinnamaldehyde/non-ionic surfactant/water system nanoemulsions were prepared using high-pressure homogenisation. The result showed that varying the cintzamaldehyde/surfactant ratio had effect significantly (p<0.05) to mean droplet diameter, polidispersity index, xi-potential, turbidity and whiteness index, while no significant effect (p>0.05) to viscosity. The mean droplet diameter ranged from 50.48 to 106.4 nm, polydispersity index from 0.06 to 0.28 and xi-potential from -4.11 to -6.98 mV. The smallest droplet size was produced using 5% cinnamaldehyde and 5% Tween 80. Response surface for droplet diameter showed that the higher the cinnamaldehyde and surfactant concentrations, the larger the droplet diameter, polydispersity index and whiteness index. However, the xi-potential increased as the cinnamaldehyde concentration decreased and Tween 80 increased. Increasing the cintzamaldehyde concentration led to an increase in turbidity. Formulation of 5% cinnamaldehyde and 623% Tween 80 gave no observable separation of the nanoemulsion with minimum droplet size, polidispersity index, viscosity, turbidity, whiteness index and maximum xi-potential in modulus. The stability of the optimum formulation was sustained for 10 days upon storage at 4 degrees C. The values of droplet diameter, PDI and xi-potential were 55.50 nm, 0.08 and -5.38 mV, respectively.