Abstract: Mixtures of maltodextrin (MD), egg yolk protein (EYP), Manchurian walnut protein isolate (MWPI) and soybean protein isolate (SPI) in different proportions were used as wall materials to prepare Manchurian walnut oil microcapsules by spray drying. The micromorphology, thermal stability, storage stability and antioxidant stability of microcapsules were analyzed. The results showed that the encapsulation efficiency of microcapsules prepared with MWPI was 73.68%, with an intact and dense structure, indicating that Manchurian walnut oil was successfully encapsulated in and protected by the microcapsules. The microcapsule powder had good flowability and solubility. The MWPI microcapsules lost only 5.48% of its initial mass under programmed heating conditions (10 ℃/min, up to 150 ℃), which was much lower than that of SPI microcapsules (10.3%), thereby being more able to meet the requirements of most thermally processed products. Microencapsulation obviously slowed down the oxidation rate of Manchurian walnut oil and improved its storage stability. The antioxidant experiments demonstrated that microencapsulation could effectively improve the antioxidant stability of active ingredients in Manchurian walnut oil. Therefore, this study demonstrated MWPI to be an excellent microcapsule wall material by evaluating its performance, which will expand the range of selection of protein-based wall materials, and provide a new idea for the application of walnut protein isolate resources to improve the added value of Manchurian walnut.

Key words: microcapsules; Manchurian walnut oil; Manchurian walnut protein isolate; wall material; encapsulation efficiency