Formulation of concentrated oil-in-water-in-oil double emulsions for fragrance encapsulation

Abstract

We report the formulation of a concentrated double oil-in-water-in-oil (O/W/O) emulsion for fragrance encapsulation. As their water-in-oil-in-water homologous, these O/W/O emulsions, seldom described in literature, also require the use of two antagonist surfactants: a hydrophilic one (HS) to stabilize the fragrance-in-water droplets and a lipophilic one (LS) to stabilize the aqueous globules dispersed in oil, containing themselves the direct emulsion. An important issue in cosmetics is the necessity to adapt the formulation to each fragrance, so that a major progress would be the successful elaboration of an O/W/O emulsion insensitive to fragrance changes. In order to approach such a composition, two model fragrances composed of 10 and 13 molecules representative of the most used molecules in this domain were specially assembled for the study. The aim was to identify possible hydrophilic and lipophilic stabilizers leading to a double O/W/O emulsions and determine compositions able to encapsulate both fragrances. The double emulsion was prepared by a two-step process, allowing varying the double emulsion composition i.e the amount of both surfactants as well as the quantity of droplets inside the globules. By plotting “feasibility diagrams” we can propose a best composition shared by the two fragrances. Such a double emulsion is composed of 20 wt% of fragrance droplets with respect to the globule volume, 75 wt% of globules with respect to the total emulsion, 7.5 wt% of HS with respect to the intermediate aqueous phase and 10 wt% of LS with respect to external oil phase. The robustness of this optimized composition against molecule changes was tested using a third fragrance. Then the encapsulated efficiency was measured showing the high encapsulation rate (close to 99 %) of the selected system and a gas chromatography analysis of each molecule composing the complex fragrance showed no alteration of the encapsulated fragrance.