Synthesis of polyampholyte microgels from colloidal salts of pectinic acid and their application as pH-responsive emulsifiers

A novel method for obtaining cross-linked micro- gels ofapple pectin has beenintroduced. Thismethodisbased on the Ugi four-component condensation in colloidal suspen- sions of pectinic acid and amines. Using various processing parameters (the polysaccharide concentration, the type and density of crosslink, and the optimal pH range), particles with controlled colloidal properties have been obtained. Lightly cross-linked polysaccharide chains acquire anionic character due to deprotonation of the carboxyl groups at pH9-10. Increasing the degree of cross-linking leads to a polyampho- lyte microgel, which can be protonated in acidic medium or deprotonated in basic medium. Polyampholyte microgels de- rived from apple pectin have proved to be an effective Pickering emulsifier at low concentrations and pH2-3, form- ing stable oil-in-water emulsions. These Pickering emulsions exhibited pH-responsive behavior: raising the solution pH to 10 resulted in immediate demulsification due to the destabili- zation of microgel network at the oil-water interface.