Ultrasound-mediated fucoxanthin rich oil nanoemulsions stabilized by κ-carrageenan: Process optimization, bio-accessibility and cytotoxicity

[Display omitted] •Seaweed oil-in-water nanoemulsions was developed by ultrasonication technique.•Formulation state was optimized using response surface methodology (RSM).•RSM was used to find best conditions of size and functional properties of emulsion.•Optimal condition (OC) was amplitude of 87 µm, 394 s, 60 °C, and 50% duty cycle.•OC was characterized and checked for its in vitro digestion, cytotoxicity assay. This work aims to produce and optimize a κ-carrageenan-based nanoemulsion (NE) to encapsulate seaweed oil, which is rich in fucoxanthin (FX), using ultrasound-assisted emulsification. κ-Carrageenan was produced using subcritical water, and seaweed oil was extracted using supercritical carbon dioxide with sunflower oil as the co-solvent. Response surface methodology (RSM) was used to understand the influence of several process parameters such as ultrasound amplitude, time, temperature, and duty cycle to produce an NE. The RSM factor was used to focus on droplet size, polydispersity index, zeta potential, viscosity, antioxidant, FX, encapsulation efficiency, and emulsion stability. Our outcomes suggested that the ultrasound process had a noteworthy influence on the NE. The best conditions to obtain an NE were an ultrasound amplitude of 87 µm, a sonication time of 394 s, a temperature of 60 °C, and a duty cycle of 50%. The resulting NE was studied by UV–Vis, Fourier-transform infrared spectroscopy, thermal gravimetric analysis, differential scanning calorimetry, scanning electron microscopy, atomic force microscopy, and X-ray diffraction. Moreover, the NE obtained from optimized conditions was checked for fatty acid content, color, oxidative stability, in vitro digestion, bioaccessibility of FX, and cytotoxicity. The results obtained suggest that lower droplet size of the emulsion can improve oxidative stability, in vitro digestion, bioaccessibility of FX, and good cell inhibition against a few cell lines. Therefore, a κ-carrageenan-stabilized NE can be used as a potential delivery system to endorse applications of seaweed oil, which is rich in FX, in functional foods, beverage systems, and pharmaceuticals.