Optimized Extraction of Saponins from Camelia Oleifera Using Ultrasonic-Assisted Enzymes and Their Surface Performance Evaluation

Tea saponin is a kind of natural non-ionic surfactant. Saponins were extracted from tea seed cake using an ultrasonic-assisted enzymatic method. The optimization of the tea saponin extraction procedure was conducted by using the response surface method to increase the yield. Study results indicated that the maximum yield of tea saponin was 69.81 mg/g under the optimum conditions of an enzyme concentration of 0.67%, a solvent-to-material ratio of 16.82 mL/g, an extraction temperature of 58.14 °C and an extraction time of 1.89 h. The surface activity experimental study results indicated that the critical micelle concentration of tea saponin was 0.5 g/L at 30 °C, and the lowest surface tension was 39.61 mN/m. The surface tension and CMC of tea saponin remained basically unchanged between 30 °C to 60 °C. When the pH of the solution was slightly acidic, the surface tension of tea saponin decreased significantly, while the CMC remained almost unchanged. Tea saponin has good salt and hard water resistance, and its surface tension decreases to a certain extent in both saltwater and hard water. The foam volume of tea saponin can reach 490 mL, with a half-life of 2350 s, and the foam is relatively stable. The combination of tea saponin and other surfactants has a certain synergistic effect. The critical micelle concentration of its complex system with the natural surfactant rhamnolipids can increase by 69.23%, and the surface tension can be reduced to a minimum of 22.56 mN/m. Moreover, by using the proposed method, the foam performance and stability of the system have been improved to a certain extent. This has significant practical significance for fully utilizing and developing waste camellia dried cake resources.