Construction of enzymatic crosslinking beta-lactoglobulin-camellia oil emulsion gels: microstructural characterization, stability, and curcumin delivery behavior

Protein-based emulsion gels with transglutaminase (TG)-catalyzed crosslinking exhibit great potential for delivering hydrophobic bioactive substances. However, effects of TG-catalyzed crosslinking modifications under different reaction times on the structural and textural characterization, stability, and delivery behavior have rarely been reported. This study investigated the effect of TG-catalyzed crosslinking on the physicochemical, structural, and functional properties of β-lactoglobulin (β-LG) - camellia oil (CAO) emulsion gels by cold-gelation under different reaction times. Results revealed that prolonged reaction times could improve the formation of intramolecular and intermolecular covalent bonds between lysine and glutamine residues. Rheological analysis showed an increase in both the storage modulus (G’) and loss modulus (G’’), indicating enhanced the gel elasticity and stability. Furthermore, the oxidative stability, the water-holding capacity, and functional stability (freeze-thaw, UV-light, thermal, and salt stability) of the emulsion gels were enhanced by the TG-catalyzed crosslinking. In the in vitro digestion process, the encapsulation efficiency and bioaccessibility of curcumin (Cur) were enhanced in the TG-catalyzed crosslinking β-LG-CAO emulsion gel system when the reaction time exceeded 3 h. The dense gel structure, improved stability, and great Cur delivery behavior of the emulsion gel could be formed by TG-catalyzed crosslinking at 4 h. This study benefited the encapsulation and release behavior of Cur in oil-in-water emulsions and the application in food and nutraceutical products.