Fabrication and characterization of dihydroquercetin microcapsules stabilized by quinoa protein–sodium alginate coacervates

The microcapsules were fabricated using the complex coacervation of quinoa protein (QP) and sodium alginate (SA) to protect the biological activities of dihydroquercetin (DHQ). The optimum preparation conditions of DHQ microcapsules were determined by zeta potential, turbidity, encapsulation yield (EY), encapsulation efficiency (EE) and loading capacity (LC) of DHQ. The physicochemical properties including microstructures, driving forces, thermal stability, storage stability and antioxidant capacity of DHQ microcapsules were characterized. The results showed that the DHQ microcapsules obtained optimum EY (59.59 ± 0.41%), EE (74.48 ± 2.49%), and LC (1041.51 ± 15.56 µg/g) at pH 3.2, the core-to-wall ratio of 1:2 (w/w), the QP-to-SA ratio of 10:1 (w/w) and the homogenization speed of 12,000 r/min. Moreover, DHQ was successfully encapsulated by QP–SA coacervates in an amorphous state and the DHQ microcapsules showed a spherical multi-core structure with compact and rough surface. It was demonstrated that hydrophobic interactions, hydrogen bonds and electrostatic interactions participated in the formation of QP–SA coacervates. Furthermore, microencapsulation could enhance the thermal stability of DHQ and preserve its antioxidant capacity. The retention rate of DHQ in microcapsules was 81.01 ± 10.54% after 3 weeks at 4 °C. These findings provided theoretical guidance for using effective wall materials to encapsulate hydrophobic bioactive substances like DHQ.