Abstract: Fish oil nanoemulsions and microcapsules stabilized by soy protein isolate (SPI) and phosphatidylcholine (PC) were prepared by three homogenization methods including high-pressure homogenization, cavitation jet homogenization and ultrasonic treatment. To evaluate the effect of homogenization processes on the physicochemical properties of fish oil nanoemulsions and microcapsules, the particle size, zeta-potential, stability, viscosity and emulsification yield of nanoemulsions were determined, together with microcapsule morphology, physicochemical properties and stability. The results indicated that the nanoemulsion prepared by cavitation jet had a small average particle size and exhibited high emulsification yield and high stability. Highly soluble microcapsules were obtained by 10 min cavitation jet with an encapsulation efficiency of 87.44%. The surface morphology of the microcapsules was full and dense without any cracks or voids and they had good oxidative and thermal stability. The nanoemulsions prepared by high-pressure homogenization and ultrasonic treatment had larger average particle size, lower emulsification yield and lower emulsion stability. The encapsulation efficiencies of the microcapsules obtained by high-pressure homogenization at 100 MPa and ultrasonic treatment at 400 W were 80.36% and 78.64%, respectively. The solubility of these microcapsules was lower than that of the microcapsules prepared by cavitation jet. In addition, micropores and larger pores appeared on the surface of the microcapsule particles, respectively, both of which had poor oxidative and thermal stability. The results obtained by Fourier transform infrared spectroscopy showed that all three homogenization processes provided high encapsulation efficiency. The fish oil nanoemulsion and microcapsule prepared by cavitation jet homogenization were superior to the counterparts prepared by the other two methods in product performance. This study can provide a theoretical basis for the selection of homogenization processes for the preparation of fish oil nanoemulsion and microcapsule products and the construction of an evaluation system for their application.

Key words: fish oil; nanoemulsion; microcapsule; homogenization