Switchable pH-responsive Pickering stabilizers made by sonothermal glycation of sodium caseinate with κappa- carrageenan

Abstract

Abstract Food-approved colloidal particles that can construct stable emulsions, but destabilize on purpose using a specific stimulus like pH change would be of great importance to food and pharmaceutical industries (bioactive delivery). However, such edible Pickering stabilizers are quite rare, since they must possess superb interfacial activity (rapid, strong and reversible adsorption at oil-water interface) to be efficient in stabilization of these unique systems. Herein, we report the formation of sodium caseinate (SC)-κappa-carrageenan (kC) colloidal conjugates that can offer such Pickering ability. SC-kC conjugates were prepared by wet-heating Maillard reaction after sonication pre-treatments (400 W, 20 kHz) for 10, 20, and 30 min. The SC-kC conjugation was confirmed by Fourier transform infrared spectroscopy, CD spectra, intrinsic fluorescence analysis, and glycation degree (GD). With increased sonication duration, a higher GD (59.75 ± 0.69% in 30 min) was observed which led to improved interfacial activity (higher adsorption quantity and rate at interface), lower particle size (< 500 nm) as well as higher emulsifying activity and stability indices. It was observed that the emulsion prepared with the 30 min ultrasonic conjugate had the lowest mean droplet size (1.65 ± 0.10 µm) and polydispersity index (0.46 ± 0.00) along with the highest zeta potential (-35.76 ± 0.54 mV). Furthermore, it was found that sonothermal glycation with kC empowered the SC to fabricate emulsions with excellent pH-responsive behaviors where it can be easily switched on (pH = 7) and off (pH = 4.5) over 4 cycles and remain stable with further emulsification. Therefore, SC-kC colloidal conjugates can create novel Pickering systems with attributes desired to many applications.