FUNCTIONAL INGREDIENTS


67


Figure 2: Emulsion droplet size of 5% oil-in-water system without surfactant. Negative control without microfibrillated cellulose (left) and utilising 0.4% active level microfibrillated cellulose as an emulsifier (right)


key challenge for the emulsifier-free category is achieving formulation stability alongside desirable textures and skin feel.14


Emulsifier-free systems Microfibrillated cellulose offers a skin-friendly alternative to emulsifiers, with the capability to suspend oil droplets in a continuous water phase in a totally emulsifier-free system. Cellulose is an amphiphilic polymer,


allowing it to act as an emulsifier and stabiliser. All morphological forms of cellulose demonstrate an intrinsic amphiphilic nature, self-assembling at oil-water interfaces,3,15,17 providing steric repulsion to prevent coalescence and stabilise oil-in-water emulsions without the need for surfactants.15 Although some particle-based cellulose


derivatives, such as microcrystalline cellulose, can exhibit ‘colloidal surfactant’ behaviour and form Pickering emulsions, due to their amphiphilic nature, wettability and adsorption at fluid interfaces, reducing the interfacial tension;16,17


found to have a greater ability to stabilise emulsion and foams than synthetic spherical particles.3


fibrillated cellulose does not form a


Pickering emulsion as its structure is not rigid.3 Materials with high aspect ratios have been


The fibrillation processes produces


extremely thin cellulose fibres, but does not chop the length of these fibres, resulting in incredibly long but thin fibres with a very high aspect ratio, making microfibrillated cellulose and ideal material to stabilise oil-in-water droplets in an emulsifier-free system. Microfibrillated cellulose offers a two-


pronged approach to emulsion stabilisation. Not only do the microfibrils adsorb at the oil-water interface,15


but at higher concentrations, the


excess non-adsorbed fibrils form an entangled 3D network throughout the aqueous continuous phase,15


preventing movement of the oil droplets,


thus preventing coalescence and further enhancing emulsion stability (and Figure 3). Due to the high shear thinning nature, all of


these stabilisation benefits are offered without noticeable increase in viscosity (viscosity is


www.personalcaremagazine.com April 2025 PERSONAL CARE


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