2024-03-29T11:58:18Zhttps://riubu.ubu.es/oai/requestoai:riubu.ubu.es:10259/60882022-11-08T13:31:41Zcom_10259_4244com_10259_5086com_10259_2604col_10259_4245
00925njm 22002777a 4500
dc
Benito Román, Oscar
author
Blanco Alcalde, Beatriz
author
Sanz Díez, Mª Teresa
author
Beltrán Calvo, Sagrario
author
2020-12
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 a
semicontinuous extractor (2.5 mL/min; 105–180 C; 5 MPa). The extraction of flavonoids resulted to
be fast (<30 min) and temperature sensitive (maximum at 145 C; total flavonoids, 27.4 0.9 mg/g
dry OSW (DOSW)). The experimental results were fitted to theWeibull model. The influence of the
solvent properties on the flavonoids quantification was found to be critical. A precipitate was formed
once the extracts cooled down. If removed, a significant fraction of the high temperature extracted
flavonoids (as much as 71%, at 180 C) was lost. Such a condition a ected especially those compounds
that show extremely low solubility in water at room temperature, whereas quercetin glycosylated
derivatives were less a ected by the polarity change of the medium induced by the temperature
change. It was demonstrated that it is necessary to re-dissolve the subcritical water extracts by
the addition of ethanol, which led to a medium with a polarity equivalent to that obtained with
water 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 high
added value bioactive compounds from OSW the principles of circular economy were fulfilled,
providing a new use for this agricultural waste.
2076-3921
http://hdl.handle.net/10259/6088
10.3390/antiox9121233
Onion
Extraction
Subcritical water
Quercetin
Polarity
Valorization
Subcritical water extraction of phenolic compounds from onion skin wastes (Allium cepa cv. horcal): effect of temperature and solvent properties