Development and Optimization of Beeswax–Coriander Essential Oil-Based Nanostructured Lipid Carriers for Encapsulation of Anthocyanin-Rich Barberry Extract

Nanostructured lipid carriers (NLCs) are colloidal delivery systems developed to address the low stability and limited bioavailability of sensitive active compounds. In this study, anthocyanin-rich barberry extract-loaded NLCs were prepared by a water-in-oil-in-water double emulsion method, using beeswax as the solid lipid and coriander essential oil as the liquid lipid. A combined D-optimal mixture design was employed to evaluate the effect of surfactant ratios (Tween 80/Tween 20 and polyglycerol ester (PGE)/polyglycerol polyricinoleate (PGPR)) on particle size, polydispersity index (PDI), zeta potential, and encapsulation efficiency. The optimized formulation suggested by Design-Expert® software was obtained at 90/10 Tween 80/Tween 20 and 90/10 PGE/PGPR ratios and showed a particle size of 94.25 nm, PDI of 0.18, zeta potential of −23.4 mV, and encapsulation efficiency of 74%. The experimental values were in close agreement with the predicted responses. TEM observations indicated spherical morphology at the nanoscale, while FTIR, DSC, and XRD analyses confirmed successful incorporation of barberry extract into the lipid matrix and a less ordered crystalline structure. During one month of storage, the optimized NLC was more stable at 4 °C compared with 25 °C and showed higher antioxidant activity than the free extract. It also exhibited a higher inhibitory effect against S. aureus and E. coli than the free form in MIC and MBC assays. Overall, the developed NLCs could serve as an effective carrier system to improve the stability of anthocyanin-rich barberry extract and extend its application in food formulations.