Colloidal Particles for Pickering Emulsion Stabilization Prepared via Antisolvent Precipitation of Lignin-Rich Cocoa Shell Extract

Abstract

This study concerns the preparation and functionality testing of a new class of Pickering particles for food emulsion stabilization: colloidal lignin-rich particles (CLRPs) derived from ethanol-soluble extract of cocoa shell. A further goal was to achieve Pickering functionality without the need to add co-emulsifying surfactants during emulsion processing. Cocoa shell is a co-product of the food manufacturing industry. As such it is anticipated that the particles would be accepted as a natural food ingredient, provided no harmful solvents are used in any step of their processing. The cocoa shell particles were milled, dispersed in water and exposed to 250 °C for 1 h in a stainless-steel tubular reactor followed by ethanol extraction to obtain a lignin-rich extract (46% (w/w) lignin with the remainder predominantly lipids). CLRPs were then fabricated by the precipitation of ethanol-dissolved extract into water (antisolvent). By employing an agitated process and droplet dosing into a non-agitated process, four particle suspensions of a range of submicron diameters were obtained. All particle suspensions contained the same mass fraction of extract and were surface active, with surface tension decreasing with increasing particle size. The smallest particles were obtained when lipids were removed from the extract prior to particle processing. In contrast to the other four particle suspensions, this one failed to stabilize a 10% (w/w) sunflower oil-in-water emulsion. We hypothesize that the phospholipids indigenously present in these CLRP formulations are a critical component for Pickering functionality. It can be concluded that we have successfully introduced a new class of Pickering particles, fabricated from an industry co-product and anticipated to be food grade.

Emulsions in Bitumen Froth Treatment and Methods for Demulsification and Fines Removal in Naphthenic Froth Treatment: Review and Perspectives

“…Moreover, literature reports that the effective IFT of the solid-adsorbed film decreases in some cases, similar to the mechanism by which emulsions are stabilized by the surfactants. 4,62 However, IFT reduction is not necessarily observed in all types of Pickering emulsions, and other stability mechanisms may be prevalent in solid-adsorbed emulsions.…”

“…Several factors influence the adsorption and positioning of the solid particles in the emulsion medium. These include the fines content, size of the solid particles in relation to the size of the droplets, wettability of the solids, interaction potential of the particles with asphaltene, oil composition and polarity, water chemistry, variation of pH in the aqueous phase, and bulk fluid viscosity, among others. − Figure illustrates the adsorption of solids in competition with asphaltenes at the oil–water interface and shows the mineralogy and morphology of the solid particles in the bitumen froth.…”