Preparation and digestibility of fish oil nanoemulsions stabilized by soybean protein isolate-phosphatidylcholine

Fish oil is used for its numerous health and nutritional benefits. Nevertheless, it is unstable during production, storage, and application. Nanoemulsions can be used as an effective carrier for encapsulated nutraceuticals. The effects of different components on the stability of fish oil nanoemulsions with soybean protein isolate-phosphatidylcholine (SPI-PC) were studied by characterizing particle size, polydispersity index, zeta-potential, turbidity, and turbiscan stability index. The SPI-PC nanoemulsions with optimal stability were prepared with 2% SPI, 0.2% PC, 1.5% fish oil, and 100 MPa homogenization pressure. Confocal laser scanning microscopy verified that the oil droplet was encapsulated inside the nanoemulsions. Compared with a Tween 20 nanoemulsions control group, the SPI-PC nanoemulsions have better storage and oxidative stability, and have better resistance to certain concentrations (0.1-0.5 M) of Na+. However, we found that the SPI-PC nanoemulsions resistance to acidic conditions was not as good as that of Tween 20. The SPI-PC nanoemulsions showed aggregation of droplets during in vitro gastric digestion while the Tween 20 nanoemulsions did not. The release rate of free fatty acids (FFA) reached 86.8% in the 2 h in vitro intestine digestion. SPI-PC nanoemulsions significantly increased the digestibility of fish oil compared with Tween 20 nanoemulsions. Hence, SPI-PC nanoemulsions could be a good way to stabilize fish oil and improve digestibility under simulated gastrointestinal conditions.