Sodium caseinate/gellan gum emulsion gels for zeaxanthin dipalmitate delivery: Preparation, characterization, and gelation mechanism.

The emulsion gel composed of proteins and polysaccharides exhibits significant potential as a targeted delivery system for bioactives in the gastrointestinal tract. In this study, a composite emulsion was prepared by using sodium caseinate (NaCas) and gellan gum (GG), which was subsequently crosslinked with transglutaminase (TG), glucono-δ-lactone (GDL), and calcium ions (Ca) to form emulsion gels. The physicochemical properties of the NaCas/GG emulsion gels were characterized to verify the effects of zeaxanthin dipalmitate encapsulation and protection, and a possible mechanism was discussed. The appearance and microscopy analyses revealed that the Ca-induced NaCas/GG emulsion gel exhibited superior shape retention and a denser network structure compared to GDL or TG crosslinking methods. The rheological analysis demonstrated that the Ca-crosslinked emulsion gels had higher modulus and hardness than their TG- or GDL- crosslinked counterparts. Infrared spectroscopy, molecular docking, and gelling force analysis revealed that the gelation mechanism of these emulsion gels primarily involved carbonyl-amide group crosslinking reactions, hydrogen bonding, and hydrophobic interactions. Furthermore, the Ca-crosslinked emulsion gel encapsulating zeaxanthin dipalmitate exhibited excellent thermal stability, resistance to gastrointestinal conditions, and stability. Overall, the above findings highlight that using Ca crosslinking in NaCas/GG composite emulsion yields edible composite materials with enhanced functional performance, thereby expanding the possibilities for food gel design strategies.