Design of Nanoemulsions through Combination of Fixed-Volatile Oils

The aim of study was to comparatively evaluate emulsions containing volatile oils e.g. peppermint oil, optamint and tea tree oil, and those containing the combination of volatile oils with soybean oil. The emulsions were prepared and then characterized by monitoring of particle size, visual observation of creaming and cracking, and zeta potential measurement. The results showed that particle size of emulsions containing only volatile oils was in the micron range (3-10 mm). However, the particle size was decreased to less than 300 nm after incorporation with soybean oil (1:1 by weight), suggesting the formation of nanoemulsions. The nanoemulsions containing both volatile oils and soybean oil demonstrated almost 100% creaming and did not show any evidence of cracking. Additionally, percent creaming and particle size were not significantly changed even after accelerated stability testing. The results indicated the good physical stability. The stabilization of emulsion might relate with the high surface charge as observed by higher zeta potential of emulsions prepared from volatile oils combined with soybeans oil. Glycerides from soybean should give more negative charge to the oleaginous phase that help preventing aggregation of oil droplets and thus increased the stability of nanoemulsions. In conclusion, the results from this study could provide the basic guideline for preparation of stable nanoemulsions for food, cosmetic and pharmaceutical fields in the near future.