Fabrication of gelatin-EGCG-pectin ternary complex stabilized W/O/W double emulsions by ultrasonic emulsification: Physicochemical stability, rheological properties and structure

Double emulsions have very promising application prospects in the pharmaceutical, cosmetic, and food industries. Nevertheless, its usage in the food industry is restricted mainly due to its immense stability problems. Here, W-1/O/W-2 double emulsion was prepared by two-step emulsification method using ultrasonic emulsification technology. The physicochemical stability, rheological properties, thermal stability, and microstructure of the double emulsion were investigated. The results revealed that W-1/O/W-2 double emulsion with optimum stability was prepared on the parameters that the ratio of W-1 (gelatin)/O primary emulsion to the external aqueous phase (gelatin-EGCG-high methoxyl pectin ternary complex) was 6:4, ultrasonic power was 80 W, ultrasonic time was 6 min, and ternary complex concentration was 0.75%. The double emulsion produced under these conditions had the smallest particle size (1143 nm) and the maximum absolute zeta potential value (39.17 +/- 0.50 mV). The results of full-featured stability analyzer manifested that the emulsion system no longer underwent phase separation. Confocal laser scanning microscopy (CLSM) successfully observed a uniformly dispersed double emulsion. Furthermore, dynamic rheological properties demonstrated that the cohesive strength of W-1/O/W-2 double emulsion was strength than that of W-1/O primary emulsion. Differential scanning calorimetry (DSC) analysis suggested that both remained stable throughout the temperature change, while the W-1/O/W-2 double emulsion was more thermally stable. Hence, the gelatin-EGCG-high methoxyl pectin ternary complex can act as an effective emulsion stabilizer to stabilize the W-1/O/W-2 double emulsion.