Emulsion Gels Stabilized Using Sweet Almond Expeller Globulin Modified by Ultrasonication Assisted with Chlorogenic Acid Conjugation: Preparation, Characterization, Stability, and Applications in Curcumin

Almond expeller is high in protein content and produced in large quantities every year; however, its utilization in the food industry remains limited. To provide new strategies to enhance the performance of protein-based emulsion gels and expand the applications of sweet almond expeller globulin (SAEG) in the food industry, emulsion gels were formed using sweet almond expeller globulin modified by ultrasonication and chlorogenic acid conjugation (SAEG-UCA) in this study. The results showed that ultrasonication and chlorogenic acid grafting improved the emulsifying capacity (from 67.51 to 143.65 m2/g) and emulsion stability (from 70.37% to 87.18%) of SAEG by increasing its solubility and interface sorption capacity and enhancing the zeta potential within the emulsion (p < 0.05). Compared with the SAEG-emulsion gel, the SAEG-UCA-emulsion gel exhibited a more compact and denser gel structure, higher crystallinity (30.71%), bound water content and viscosity, and superior rheological stability (lower loss factor) and elasticity. Furthermore, the SAEG-UCA-emulsion gel showed superior oxidative stability, and higher chewiness (32.35 g), springiness (0.77), hardness (78.63 g), and cohesiveness (0.72) than SAEG-emulsion gel. Additionally, the SAEG-UCA-emulsion gel improved the photostability, encapsulation and loading capacities, and bioaccessibility of curcumin (p < 0.05). However, more specific mechanisms should be investigated in future research.