Incorporation of Nettle (Urtica dioica L.) Hydrophilic Actives in Alginate Beads: Design of Formulation, Encapsulation Efficiency, Antioxidant Activity and Characterization of Beads

In this study, nettle (Urtica dioica L.) bioactives were extracted using an environmentally friendly method and then encapsulated in alginate via ionic gelation. The research aimed to optimize encapsulation efficiency (EE), antioxidant activity (in vitro 2,2-diphenyl-1-picrylhydrazil scavenging activity), and bead morphology (sphericity factor [SF] and roundness [Rn]) with Box-Behnken design under the response surface method based on three parameters (CaCl₂ and sodium alginate concentration, and time). The optimal points were determined as almost 12% CaCl₂, 2% alginate, and 10 min for bead hardening in order to obtain the best quality product (31.52% of EE, 7.31 mg-TEAC/g-DB of antioxidant activity, 0.01 of SF and 0.804 of Rn). The most critical factor of EE and Rn was hardening time at p < 0.0001, while sodium alginate concentration was the most significant factor for antioxidant activity and SF at p < 0.0001. The findings demonstrate that the proposed method is practical and efficient in producing nearly spherical and stable beads with significant antioxidant properties. This work highlights the potential for alginate-based microencapsulation to enhance the stability and functionality of plant-derived bioactives.