Waterless EC oleogels as innovative cold-cold emulsion bases

Replacing cosmetic emulsions with waterless alternatives is desirable from a sustainability perspective, but doing so directly is challenging due to textural and sensory limitations. Ethylcellulose (EC) is an oleogelator with emulsifying properties, which could provide an indirect solution to this challenge. This project investigated whether EC oleogels could serve as innovative emulsion bases for sustainable cold-cold emulsification.

EC oleogels were prepared by mixing EC, selected emollients and, if applicable, emulsifiers at 140º C. Obtained oleogels were emulsified with water at various ratios and phase temperatures via high shear dispersion. Samples were tested rheologically by shear rate sweep (0.1 – 200.00 s-1) and amplitude sweep (1.0 – 500.0 Pa; 1.00 Hz) methods, using an oscillatory rheometer with a parallel plate geometry. An immersion/de-immersion method using a texture analyser was employed to test the textural parameters of selected samples.

Combining EC with Castor Oil (CO) was essential to obtain stable oleogels and, in turn, stable emulsions. Diluting CO with other vegetable or synthetic emollients (Linseed Oil, C12-15 Alkyl Benzoate and Caprylic/Capric Triglycerides) was important to optimise emulsion viscosity. Incorporating both Sorbitan Monostearate and Polysorbate 60 has achieved the following: (1) lowered emulsion yield point and resulted in predominantly elastic systems at low stresses that transitioned to predominantly viscous systems at higher stresses and (2) increased spreadability and notably reduced stickiness, thus achieving properties typical of cosmetic emulsions.

This study has shown for the first time that EC oleogels can be successfully used as cold-cold emulsion bases, thus reducing thermal energy consumption. They could serve as waterless bulk products, to be extemporaneously and locally transformed into consumer-acceptable emulsions.