Development of casein-based nanonutraceuticals by entrapping anthocyanin derived from secondary-agricultural residues: a step towards functional food additives†

This study aims to extract anthocyanins (ACNs) from different secondary-agricultural residues and encapsulate them using casein to enhance their stability and bioavailability. Ultrasonic-assisted and conventional extraction methods yielded substantial anthocyanin content from black plum (BP), blueberry (BB), and black wheat bran (WB). After purification, ACNs were encapsulated with casein through the desolvation technique. The optimized anthocyanin-casein-based nanoparticles (A-CNPs) resulted in satisfactory size, polydispersity index (PDI), and zeta potential values of 196–201 nm, 0.184–0.241, and −36 to −34 mV, respectively. BB@A-CNPs resulted in the highest encapsulation efficiency of 92% compared to BP@A-CNPs (83%) and WB@A-CNPs (72%). BP@A-CNPs, WB@A-CNPs, and BB@A-CNPs exhibited high storage stability for 28 days. A-CNPs, particularly BB@A-CNPs, exhibited improved stability towards temperature, pH change, and light. Furthermore, the gastrointestinal stability and release of ACNs from BB@A-CNPs were also assessed using an in vitro digestion model. The controlled release of ACNs and the high antioxidant activity of the final digest suggest improved bioavailability of BB@A-CNPs. Thus, BB@A-CNPs can be used as functional food additives for potentially enriching dairy products with health-promoting anthocyanins. These findings support further development and in vivo validation of the application of these nanonutraceuticals as food additives.