Enhanced Microencapsulation of Quercetin-Rich Onion (Allium cepa) Peel Extract in Ethyl Cellulose Using a W/O/W Double Emulsion: Optimised Production, Characterisation, and Controlled Release

Quercetin (QE) is an important phenolic that offers various health benefits. This compound can be extracted from onion (Allium cepa) peels, a common agro-industrial by-product, resulting in quercetin-rich extracts (QRE). However, incorporating QE and QRE into foods and other products remains limited due to their low stability and solubility. Thus, this study aimed to microencapsulate QE and QRE using ethyl cellulose as wall material and double-emulsion as encapsulation technology to enhance their stability and bioavailability. The effect of different formulation and production parameters was studied to optimise the final formulation and assess their influence on the final characteristics. The oil phase solvent was the most significant variable influencing the encapsulation efficiency (EE), actual loading content and particle size. The QRE was obtained from onion peels and characterised, exhibiting a total phenolic content of 362 mg_GAE∙g_extract^-1 and interesting antioxidant properties. The anti-diabetic potential was demonstrated by inhibiting 91 and 90% of α-amylase and β-glucosidase, respectively. The QRE was microencapsulated using the two most effective formulations and compared with the quercetin-loaded microparticles. Extract-loaded microparticles performed similarly to quercetin-loaded microparticles, with EEs between 90 and 97% and an average particle size of around 19 μm. In vitro release studies were conducted in ultrapure water and octanol. Results indicated that the primary release mechanism in both media was Fickian diffusion, and higher loading resulted in a faster release into the medium. This study provided new and innovative insights into the microencapsulation of bioactive QE, whether pure or from agro-industrial by-products, for incorporation into various value-added products.