Chitin nanocrystal/carboxymethyl cellulose bilayer emulsion with rigid inner layer and flexible outer shell for ultra-stable encapsulation of fish oil.

The polyunsaturated fatty acids in fish oil are prone to oxidation and have poor dispersibility, which limits their use in the food sector. In this work, oil-in-water emulsions stabilized by chitin nanocrystals (ChNC) were prepared via high-speed homogenization. Anionic carboxymethyl cellulose (CMC) was assembled onto cationic ChNC-stabilized emulsion droplet surfaces via layer-by-layer self-assembly technology to construct ChNC/CMC (Ch-C) bilayer emulsions with rigid inner layer and flexible outer shell structures. The results of dynamic light scattering proved that the CMC could significantly reduce the emulsion droplet size. The root mean square roughness and arithmetic mean roughness of the emulsion droplets decreased from 10.5 and 8.4 nm to 5.6 and 4.4 nm with increasing CMC concentration, respectively. The droplet size distribution curve of the Ch-C emulsion with the CMC concentration of 1 % (Ch-C-4) after 30 days of storage changed little compared with the initial state, showing excellent storage stability. In addition, the Ch-C-4 emulsion was stable over the wide pH range (2-6), high temperature (90 °C), and high ionic strength (400 mM). Furthermore, compared with ChNC emulsion, the primary and secondary oxidation contents of Ch-C-4 decreased by 11.9 % and 23.7 %, respectively, suggesting that Ch-C bilayer emulsion can effectively delay the oxidation of fish oil. Therefore, this study proposes new research strategies for the design of polysaccharide-based bilayer emulsions and the protection of functional lipids.