Coating of colloidal lignin particles with sodium caseinate and thereof application in Pickering emulsions

Colloidal lignin particles (CLPs), derived from ubiquitous dietary fiber, are emerging as viable emulsifiers due to their sustainability and biocompatibility. Despite appealing advantages, the emulsifying capacity of CLPs in triglyceride matrices (e.g. edible oil) is constrained by their inadequate amphipathic properties. As characterized by intermediate wettability and renewable provenance, sodium caseinate (Cas) is proposed as a promising surface modifier to enhance the interfacial performance of CLPs. This study conscientiously delved into the adsorption dynamics of Cas onto CLPs and elucidated the ramifications of Cas coating on the physicochemical attributes of CLPs and consequent sunflower oil-loaded emulsions. The presence of non-covalent forces was a crucial factor in consolidating the chemisorption of Cas onto CLPs, where hydrophobic interactions exerted the major contribution. Progressive increments of Cas coating were observed to enhance particle size and hydrophobicity while diminishing the absolute surface charge of the colloidal entities, thus bolstering their interfacial affinity accompanied by distinct adsorption behaviors. As a result, Cas molecules improved the stability of CLPs-based Pickering emulsions mainly by thick interfacial layers and fortified network structures. With the highest level of curcumin retention observed in the 0.16Cas-CLPs emulsion, the encapsulated systems stabilized by modified CLPs effectively protected photosensitive compounds against ultraviolet irradiation.