RT info:eu-repo/semantics/article T1 Subcritical water extraction of phenolic compounds from onion skin wastes (Allium cepa cv. horcal): effect of temperature and solvent properties A1 Benito Román, Oscar A1 Blanco Alcalde, Beatriz A1 Sanz Díez, Mª Teresa A1 Beltrán Calvo, Sagrario K1 Onion K1 Extraction K1 Subcritical water K1 Quercetin K1 Polarity K1 Valorization K1 Ingeniería química K1 Chemical engineering AB The valorization of onion skin wastes (OSW) through the extraction, identification,and quantification of phenolic compounds was studied in this work, using subcritical water in asemicontinuous extractor (2.5 mL/min; 105–180 C; 5 MPa). The extraction of flavonoids resulted tobe fast (<30 min) and temperature sensitive (maximum at 145 C; total flavonoids, 27.4 0.9 mg/gdry OSW (DOSW)). The experimental results were fitted to theWeibull model. The influence of thesolvent properties on the flavonoids quantification was found to be critical. A precipitate was formedonce the extracts cooled down. If removed, a significant fraction of the high temperature extractedflavonoids (as much as 71%, at 180 C) was lost. Such a condition a ected especially those compoundsthat show extremely low solubility in water at room temperature, whereas quercetin glycosylatedderivatives were less a ected by the polarity change of the medium induced by the temperaturechange. It was demonstrated that it is necessary to re-dissolve the subcritical water extracts bythe addition of ethanol, which led to a medium with a polarity equivalent to that obtained withwater at high temperature. At 145 C, quercetin (15.4 0.4 mg/g DOSW) and quercetin-40-glucoside(8.4 0.1 mg/g DOSW) accounted for the 90% of the total flavonoids identified. By recovering highadded value bioactive compounds from OSW the principles of circular economy were fulfilled,providing a new use for this agricultural waste. PB MDPI SN 2076-3921 YR 2020 FD 2020-12 LK http://hdl.handle.net/10259/6088 UL http://hdl.handle.net/10259/6088 LA eng NO Junta de Castilla y León (JCyL) and the European Regional DevelopmentFund (ERDF)) through projects BU301P18 and BU050P20, and by the Agencia Estatal de Investigación throughgrant number PID2019-104950RB-I00/AEI/10.13039/501100011033. OBR’s postdoctoral contract was funded byJCyL and EDRF through project BU301P18. DS Repositorio Institucional de la Universidad de Burgos RD 29-mar-2024