Using mixed non-ionic surfactants Tween/Span, we determined the required hydrophilic-lipophilic balance (HLB) value on the oil in water nanoemulsion of lemon myrtle essential oil. In this study, Span 80 mixed with Tween 80, and Span 20 mixed with Tween 20 were used as mixed non-ionic surfactant. The droplet size, polydispersity index and stability of the lemon myrtle nanoemulsion at different HLB values were obtained over a period of 28 days. Both mixed surfactants have similar required HLB value at HLB 14 due to their smallest droplet size and lowest polydispersity index during the early nanoemulsion preparation. However, after a period of 28 days, nanoemulsion with Span 80-Tween 80 surfactant mixture was more stable compared to Span 20-Tween 20 surfactant mixture. Therefore, HLB 14 using Span 80-Tween 80 surfactant mixture has been selected as the required HLB for lemon myrtle nanoemulsion due to its stability and consistency of droplet size in 28 days.
