Enhanced coalescence stability of droplets through multi-faceted microgel adsorption behaviour

Abstract

Tannic acid-crosslinking of whey protein isolate (WPI) microgels produces soft particles that can physically stabilize food emulsions. Here, these particles were used to investigate their compression at the air-water interface, and early-time stabilization of a model emulsion. Langmuir trough experiments show that the microgels have a compression behaviour similar to synthetic microgels with a core-shell structure. The dangling chains provide protein-protein interactions at low surface coverage, while the partially-flattened cores provide thicker surface patches. Microfluidic experiments showed that at low continuous phase concentration, WPI microgels suppress coalescence due to bridging, which leads to improved stability compared to emulsions stabilized by native WPI. In contrast to classic Pickering emulsions, longer adsorption times lead to higher adsorbed amounts, which is expected due to the chains on the microgel surface, and possibly flattening of these microgels at the interface. Both features together are expected to be instrumental in obtaining highly stable microgel-stabilized food emulsions. • Tannic acid-crosslinked whey protein microgels are soft and surface active particles. • For low coverage, increase of surface elasticity with pressure is similar to WPI. • Microgels stabilize emulsions more efficiently than proteins. • Emulsions are stabler when longer adsorption time is allowed for microgels. • Bridging flocculation prevents coalescence of droplets stabilized by microgels.