Extraction of the flavonol quercetin from onion waste by combined treatment with intense pulsed light and subcritical water extraction

The objective of this study was to develop a hurdle technology for maximizing the efficiency of extracting quercetin from onion waste skin by combining eco-friendly subcritical water extraction with physical pretreatment by intense pulsed light. The maximum concentration of quercetin was observed to be 17.32 +/- 1.12 mg/g onion skin at the subcritical water extraction condition of 145 degrees C for 15 min with intense pulsed light at 1200 V for 60 s; the quercetin concentration was 15.1 +/- 91.12 mg/g onion skin using subcritical water extraction alone at 145 degrees C for 15 min. The results might be attributable to intense pulsed light loosening the onion interstitial walls, which was detected by environmental scanning electron microscopy and fluorescence microscopy. This study has demonstrated that intense pulsed light is a promising pretreatment technology for enhancing the extraction of quercetin by subcritical water extraction. These results for re-utilization of products generated from onion waste would be helpful for developing sustainable, cost-effective, and efficient technologies for the reduction of food waste. (C) 2019 Elsevier Ltd. All rights reserved.