Development of Olive Oil and alpha-Tocopherol Containing Emulsions Stabilized by FucoPol: Rheological and Textural Analyses

Biobased raw materials like natural polysaccharides are increasingly sought by the cosmetic industry for their valuable properties. Such biodegradable and usually non-cytotoxic biopolymers are commonly used in skin-care products as rheological modifiers, bioemulsifiers and/or bioactive ingredients. FucoPol is a natural polysaccharide with reported biocompatibility, emulsion-forming and stabilizing capacity, shear-thinning behavior and bioactivity (e.g., antioxidant capacity, wound healing ability) that potentiate its utilization in skin-care products. In this study, olive oil and alpha-tocopherol containing emulsions were stabilized with FucoPol. Although the presence of alpha-tocopherol negatively impacted the emulsions' stability, it increased their emulsification index (EI). Moreover, FucoPol outperformed the commercial emulsifier Sepigel (R) 305, under the tested conditions, with higher EI and higher stability under storage for 30 days. The formulation of FucoPol-based emulsions with olive oil and alpha-tocopherol was studied by Response Surface Methodology (RSM) that allowed the definition of the ingredients' content to attain high emulsification. The RSM model established that alpha-tocopherol concentration had no significant impact on the EI within the tested ranges, with optimal emulsification for FucoPol concentration in the range 0.7-1.2 wt.% and olive oil contents of 20-30 wt.%. Formulations with 25 wt.% olive oil and either 0.5 or 2.0 wt.% alpha-tocopherol were emulsified with 1.0 wt.% or 0.7 wt.% FucoPol, respectively, resulting in oil-in-water (O/W) emulsions. The emulsions had similar shear-thinning behavior, but the formulation with higher FucoPol content displayed higher apparent viscosity, higher consistency, as well as higher firmness, adhesiveness and cohesiveness, but lower spreadability. These findings show FucoPol's high performance as an emulsifier for olive oil/ alpha-tocopherol, which are supported by an effective impact on the physicochemical and structural characteristics of the emulsions. Hence, this natural polysaccharide is a potential alternative to other emulsifiers.