Effect and application of spray drying and freeze drying on characterization of walnut oil microcapsules

In the current study, a walnut oil (WO) emulsion was prepared with WO as the core material and sodium caseinate and maltodextrin as the wall materials. The effects of spray drying (SD) and freeze drying (FD) on the structure and quality of WO microcapsules were compared, and the role of WO microcapsules as a substitute for commercial creamer in coffee was investigated. The results demonstrated that the WO microcapsules prepared by the SD method had dense microstructure, spherical particles, no oil drop aggregation, small particle size, good fluidity, an embedding rate of up to 93.60%, an unsaturated fatty acid content of 87.00%, and no significant difference in thermal stability or stability of the restored emulsion compared with FD. The freeze-dried WO microcapsules have irregular structure, porous surface structure, high oil content on the surface, 76.84% embedding rate, some accumulation of droplets, large grain size, and poor fluidity. The electronic nose and electronic tongue results reveal that the microcapsules prepared by the two methods have similar flavor when applied to coffee. The spray-dried WO microcapsules are prepared with a flavor closer to that of commercial creams. In summary, microcapsules prepared by SD are superior to FD and are promising for industrial production; further, the nondairy creamer based on WO has great potential for coffee application.