Protect properties: COSSMA

Essential oils are organic compounds which are naturally produced by plants and their properties largely depend on their plant of origin. Their direct use in cosmetic products is limited because they are highly volatile ingredients. Dr Danny Goldstein and Dr Shaher Duchi explain the advantages of the encapsulation.

While offering consumer and marketing benefits, essential oils are known to degrade and to lose their active efficacy, discolour easily, overpower fragrances, or emit a strong odour, thus affecting the overall product presentation.

To overcome this drawback, there are some methods on the market. One uses the encapsulation of essential oils by means of a polymer shell as a solution. Microencapsulation technologies stabilise the core material and keep it separate from environmental factors. As such, the volatility rate of essential oils is significantly controlled and reduced because the encapsulated essential oils are protected from light, air, and heat.

Rezention of eucalyptus oil in its encapsulated form, CelluOil EC microcapsules (purple bar), compared to free form (orange bar) following storage at 75°C for 52 h. Data is presented as mean %of initial content (n=3).

Balances interplay

It is important to note that microcapsules’ performance strongly depends on the physical properties of the polymeric shell as well as on the active ingredient itself and the compatibility between them. Therefore, to prepare microcapsules with the optimal functions, it is necessary to develop a preparation method which is suitable to the physical properties of both the active ingredient and polymeric shell materials being used.

Many methods have been used for the preparation of encapsulated essential oils such as interfacial polymerisation, phase inversion precipitation, in-situ polymerisation, and solvent evaporation. Next to the well-known methods, there is also novel microencapsulation process based on a modified solvent extraction method, to overcome formulations challenges. To date, there were various successfully encapsulated essential oils ranging from eucalyptus, to lavender, and geranium.

The encapsulated essential oils¹ minimise all of the aforementioned formulation obstacles by isolating the essential oils until application, while still allowing the oils to be integrated into any cosmetic product. This technology makes it possible to convert the essential oil into powder form and encapsulate about 50% of the essential oil within the microcapsules.

Integrated in the formulation

One sophisticated layer of cellulose-based polymer is used that acts as a film separating the essential oil from the rest of the formula. Once applied to the skin, the polymeric shell collapses, resulting in an immediate release of part of the essential oil while the rest diffuses over-time from the adhesive film created by the polymer on the skin.

These microcapsules exhibit an average particle size of less than 70 micron, and, due to their amphiphilic properties, they can be well distributed within both oil and water pha-ses of the cosmetic formulation. They can be mixed into O/W, W/O, water gels, serums, and even anhydrous formulations such as powders and sticks.

Such technology contributes to the improved stability and performance of the final product and opens new dimensions for formulators and product development teams designing innovative essential oils-based formulas and products.