Formation and stability of emulsions using crude extracts as natural emulsifiers from Argan shells

This study evaluated the emulsifying performance of five aqueous-ethanolic argan shell (Argania spinosa L.) crude extracts. We aim to compare crude extracts originating from the same raw material to produce stable oilin-water (O/W) emulsions. First, surface-active compounds (i.e. saponins, proteins, and polyphenols) were quantified and interfacial tension against soybean oil of the extracts was assessed. We report here that despite the variation in the composition, the crude extracts were capable of similarly reducing the interfacial tension at the soybean oil/water interface to an average of 11 mN/m. Nevertheless, when comparing oil droplets formation, the volume mean droplet size varied within extracts 200 nm <= d(4,3) <= 440 nm. The emulsions were stable for 30 days at two temperatures 5 degrees C and 25 degrees C with high negative charge - 46.3 mV <= zeta-potential <= - 51.5 mV. The stabilization mechanism is attributed to the synergic effect of surface-active compounds found in the bulk phase. The whole composition of crude extracts contributes to the overall emulsifying performance. Besides, protein and proteins-saponins complexes, adsorbing to the interface, provide electrostatic and steric repulsions that enhance the stability of emulsions.