Ionic liquid-based nanoemulsion as a promising strategy to enhance the bioaccessibility of β-carotene obtained from Dunaliella salina

Dunaliella salina is a unicellular halophile green microalga that presents the capacity to accumulate high amounts of β-carotene, a bioactive compound widely recognized by its health benefits. To fulfil its biological functions, however, β-carotene needs to be bioaccessible, which is challenging as its bioaccessibility is typically low. A promising strategy to overcome β-carotene's low bioaccessibility is its entrapment in nanoemulsions (NEs). This study evaluated the influence of a bio-based ionic liquid (IL) as an emulsifier and different lipid concentrations on both the in vitro gastrointestinal behavior of NEs and β-carotene bioaccessibility. NEs were obtained from the sequential application of the IL as a green solvent for β-carotene extraction from D. salina and as an emulsifier to stabilize the β-carotene-loaded NEs. The NEs were composed of sunflower oil (10, 20, and 30 %), 2 % extract from D. salina enriched with β-carotene and IL and water (88, 78 and 68 %), being produced by high-intensity ultrasonication. The produced NEs were evaluated regarding physical stability (droplet size, polydispersity index, and ζ-potential) and the entrapment efficiency of β-carotene during 30 days of storage. In addition, β-carotene bioaccessibility and NEs' behavior under in vitro static digestion were evaluated as well. It was observed that the increase in lipid content resulted in higher droplet size (295–337 nm), decreased ζ-potential (−66 to −50 mV) during all the storage time, and increased β-carotene bioaccessibility (11–92 %), with no significant changes observed in β-carotene entrapment. The results suggested that the entrapment of β-carotene in NEs has great potential for its protection and for increasing its bioaccessibility. • Nanoemulsions presented high stability and β-carotene entrapment efficiency. • The increase in lipid content increases the β-carotene entrapment and stability. • Nanoemulsions stabilized with bio-based ionic liquid enhance β-carotene delivery. • Nanoemulsions protect β-carotene and improve bioaccessibility during in vitro digestion. • Increased lipid content in nanoemulsions raised β-carotene bioaccessibility to 92 %.