Recuperación de polifenoles presentes en salvado de trigo y piel de cebolla mediante un proceso combinado de extracción asistida por ultrasonidos y nanofiltración

Wheat bran and onion skin waste are agri-food by-products generated in large quantities annually. Their valorization represents an important opportunity, linked to sustainability, for obtaining bioactive compounds with beneficial properties. These by-products are notable for their high content of bioactive compounds, specifically phenolic compounds, among which quercetin and ferulic acid stand out for their antioxidant activity. The main aim of this work has been to study the technical feasibility of a combined ultrasound-assisted extraction (UAE) / nanofiltration (NF) process for the recovery of phenolic compounds present in wheat bran and onion skin wastes generated as by-products in local food companies. UAE was firstly performed for the extraction of polyphenols from wheat bran (WB) and onion skin waste (OSW) using an acetate buffer at pH 5 and an aqueous ethanol solution (70 vol. %) as solvents, respectively, under the optimum operating conditions. A final WB extract was obtained with a total polyphenol content (TPC) of 3.56 ± 0.18 mg GAE/g WB and an antioxidant activity (AA) of 7.75 ± 1.20 µmol Fe2+/g WB. An OSW extract was also obtained, with a TPC of 44.47 ± 0.83 mg GAE/g OSW, a total flavonoid concentration (TFC) of 19.22 ± 0.35 mg QE/g OSW, and an AA of 28.38 ± 2.70 mg Trolox/g OSW. Ferulic acid is the main component of wheat bran extract, while quercetin and its glycosylated derivatives are the main components of onion skin extract. Both extracts were then concentrated by nanofiltration (NF) in a high pressure stirred cell, using a NF270 flat polyamide membrane (270 Da cut-off), under optimal operating conditions reaching a volume concentration ratio (VCR) of 5 after 7,5 and 1,8 h for WB and OSW extracts, respectively, with minimal loss of polyphenols in the permeates and recoveries of AA, TPC, and TFC in the concentrates higher than 99% in all cases. The results obtained in this study could contribute to the valorization of agri-food waste using environmentally friendly techniques, demonstrating the potential o

TED2021-129311B-I00 – Tecnologías verdes basadas en el empleo de fluidos presurizados para valorizar biomasa lignocelulósica mediante la producción de furfural (GREENFUR), financiado por el Ministerio de Ciencia e Innovación. PID2022-136385OB-I00 – Nuevas estrategias para la producción de ácido láctico de segunda generación empleando tecnologías emergentes basadas en fluidos presurizados (2BIOLAC), financiado por la Agencia Estatal de Investigación. BU027P23 – Tecnologías sostenibles de fluidos presurizados para valorizar subproductos de la industria agroalimentaria ricos en proteínas: nuevas estrategias, escalado y análisis tecnoeconómico y medioambiental (SOSPROTEIN), financiado por la Junta de Castilla y León y el Fondo Europeo de Desarrollo Regional (ERDF).