Food-grade W/O/W emulsion-filled sodium alginate hydrogel for co-delivery of riboflavin and curcumin

Developing environmentally friendly delivery systems capable of encapsulating, protecting, and promoting the absorption of bioactive components in the human body is crucial for those with low oral bioavailability and poor stability. This study developed W/O/W emulsion-filled sodium alginate (SA) hydrogel for the co-delivery of hydrophilic riboflavin and hydrophobic curcumin. Firstly, W/O/W emulsion was prepared using peanut protein isolate (PPI)-bacterial cellulose nanofibers (BCNFs) as the hydrophilic emulsifier and lecithin as the lipophilic emulsifier, and the effect of stabilizer concentrations on emulsion stability was investigated. Results showed that PPI and BCNFs self-assembled into stable complexes through electrostatic interaction and hydrogen bonding, thereby improving the emulsification properties of PPI. Subsequently, SA was added to the outer aqueous phase of emulsions, and its influence on emulsion properties and stabilization mechanism was investigated. SA significantly improved the stability and rheological properties of PPI-BCNFs-stabilized W/O/W emulsions. Finally, the loading capacity of this system for riboflavin and curcumin and its gastrointestinal fate were evaluated. We found this delivery system efficiently co-delivered both hydrophilic and hydrophobic bioactive components and improved their photostability and thermal stability. Moreover, the bioaccessibilities of riboflavin and curcumin were significantly increased to 61.97% and 45.66%, respectively. This was attributed to SA forming a composite interfacial layer on droplets and a dense gel network in the continuous phase, thereby acting as a physical barrier to better protect the encapsulated components. This delivery system holds promise for the development of functional foods incorporating multiple nutraceuticals.