Effect of Diacylglycerol Addition on Structure and Properties of Curcumin-Loaded Emulsion Gel Beads

To investigate the effects of diacylglycerol (DAG) addition on the structure and physicochemical properties of curcumin (CUR)-loaded soy protein isolate (SPI)-sodium alginate (SA) emulsion gel beads, these beads were prepared using DAG as the oil phase. Experimental groups were formulated with SPI solution-to-DAG mass ratios of 10:1, 10:3, and 10:5, and denoted as SS-1DC, SS-3DC, and SS-5DC, respectively. Control groups included SS-3D (without CUR), SS-C (without DAG), and SS (without either CUR or DAG). The microstructure, shrinkage ratio, water holding capacity, textural properties, freeze-thaw stability, encapsulation efficiency, and antioxidant activity of the gel beads were systematically evaluated. X-ray diffraction analysis revealed that CUR existed in an amorphous state within the gel matrix. Fourier transform infrared spectroscopy further confirmed that the incorporation of CUR and DAG did not disrupt the fundamental structure of the gel network. Analysis of physicochemical properties indicated that with increasing DAG content, the shrinkage ratio of the gel beads gradually decreased, while their water holding capacity and freeze-thaw stability significantly improved. Texture analysis showed that the introduction of DAG significantly reduced the hardness of the gel beads, with a corresponding downward trend in other textural parameters such as springiness and chewiness. Regarding encapsulation efficiency, the addition of DAG exhibited no significant effect on that of CUR. The evaluation of antioxidant activity revealed that the SS-3DC group possessed superior reducing power. However, no significant difference in DPPH radical scavenging activity was observed between the SS-3DC and SS-5DC groups. In summary, the gel beads prepared with an SPI solution-to-DAG mass ratio of 10:3 (the SS-3DC group) exhibited the optimal comprehensive performance. This study provided a theoretical reference for the construction of an emulsion gel system with the dual functional properties of DAG and CUR.