Coarsening Mechanisms of Alkane-in-Water Okra Pectin Stabilized Emulsions

The influence of emulsifier type (okra pectin extracted at low and high pH values) on coarsening mechanisms in acidic oil-in-water emulsions was studied. Ultrasound-assisted emulsification at pH 2.0 was employed in order to fabricate emulsions of smaller droplet sizes and improved stability on ageing. Emulsions were characterized by means of static light scattering, rheology and interfacial composition (e.g., adsorbed protein and pectin). Okra pectin extracted at higher pH showed greater emulsion stabilizing capacity than those extracted at lower pH values, as revealed by droplet size distribution analysis and the rate of destabilisation kinetics. Ostwald ripening was assigned as the governing destabilisation mechanism for emulsions formulated with pectin extracted at high pH. Emulsions stabilized with okra pectin extracted at low pH exhibited a rapid droplet growth, due to Ostwald ripening-induced coalescence as evidenced by the development of the DSD curves on storage. These findings show that okra polysaccharides demonstrate remarkable differences in their stabilizing properties and magnitudes of Ostwald ripening and coalescence events depending on the employed isolation protocol.