Abstract: Decapterus maruadsi fish oil is rich in unsaturated fatty acids, but it is easily oxidized, causing loss of nutritional value. Microcapsulation has emerged as one of the best strategies to prevent fish oil oxidation. In the present study, scanning electron microscopy, laser scanning confocal microscopy (LSCM), Fourier transform infrared spectroscopy (FTIR) with second derivative fitting, and pH-stat method were used to investigate the morphological structure, the interaction during the formation process and the simulated digestion characteristics in vitro of microencapsulated Decapterus maruadsi fish oil prepared by spray drying using gum arabic, gelatin and trehalose as wall materials. The results showed that the fish oil microcapsules were spherical granules with smooth and compact surfaces. Under LSCM, the fish oil microcapsules presented a mononuclear cavity structure with gelatin evenly distributed on the wall and the fish oil wrapped inside the wall. The FTIR of microcapsules revealed the characteristic absorption peaks of the wall and core materials, which confirmed the formation of an embedded structure. The α-helix content of the secondary structure of gelatin decreased after spray drying, demonstrating the occurrence of protein-protein hydrogen bonding, which enhanced the structure stability of the microcapsule structure. In vitro simulated digestion experiments showed that during the digestive process free fatty acids were released fast initially and then slowly; the accumulative release amount was 72.62% at 120 min. LSCM revealed that during digestion, the core material was migrated to the wall surface and released gradually. The above results provide theoretical data for the development, application and evaluation of microcapsule products.

Key words: Decapterus maruadsi, fish oil, microcapsule, structure characterization, in vitro digestion