Abstract:Walnut oil microcapsules were prepared using the spray drying technology to solidify β-cyclodextrin and soy protein isolate as the wall materials. Encapsulation efficiency was chosen as the evaluation index, and the optimal experimental range was determined through single-factor experiments based on core-to-wall ratio, solid content concentration, and ultrasonic power and time. Response surface experiments were then conducted to identify the best preparation process by establishing a quadratic regression equation model for the four factors mentioned above and encapsulation efficiency. The results indicated that the highest encapsulation efficiency was 73.02% under 430 W ultrasound power, 1:3 core-wall ratio, and 12.5 wt.% solid concentration. Additionally, the physicochemical properties of the walnut oil microcapsules were tested, showing excellent solubility of 86.01% and repose angle of 41.11°, indicating its good fluidity. The particle size distribution was uniform, concentrated at approximately 3 μm. Moreover, the microcapsules exhibited good thermal stability and had a stable structure below 264 ℃. Oxidative stability experiments showed that the shelf-life of walnut oil microcapsules at room temperature (25 ℃) was 174 days, significantly higher than that of 75 days for unencapsulated walnut oil. Walnut oil microcapsules prepared under the optimal conditions in this study exhibited excellent solubility and stability, thereby expanding the applications of walnut oil in food processing.
