Unravelling the emulsifying properties of unfractionated plant powders: From interface to bulk

Abstract

Crude plant-based by-product powders can stabilise emulsions. Their chemical composition varies substantially depending on both the source plant and the manufacturing process, resulting in different emulsifying properties. This diversity was assessed by studying the emulsifying properties of three chemically different by-products (apple seed cake: protein-rich, apple pomace: non-protein soluble-rich, and liquorice root: mostly water-insoluble) ground into fine and coarse powders. The properties (droplet size, particle anchoring ratio, rheological properties) of the powder-stabilised emulsions were monitored for one month and linked to powder suspensions properties assessed in the presence and absence of solid particles. The interfacial scale was emphasized as the primary location to study the interactions between mixed emulsifiers. The interfacial properties of the powders, and especially the competition between solid particles and soluble compounds, were successfully linked to emulsions properties. Protein-rich powder-stabilised emulsions contained smaller droplets, whose diameter varied slightly with particle size, confirming soluble macromolecules dominance at interfaces. With the soluble powder, particles and soluble macromolecules acted synergistically at both interfacial and bulk scales, indicating mixed interfaces. Particle size determined the properties of the emulsions stabilised with insoluble powder, suggesting interfaces mostly composed of solid particles. Solid particles ensured the gravitational and thermodynamic stability of all powder-stabilised emulsions.