A comparative study of anaerobic and aerobic decomposition of quercetin glucosides and sugars in onion at an ambient temperature

Abstract

The purpose of the study was to investigate the decomposition of onions under anaerobic and aerobic conditions. The main aim was to determine the changes in composition of quercetin-related compounds and sugars, with simultaneous analysis of total phenolics, total flavonoids and antioxidant activity. The results indicate that anaerobic conditions lead to the deterioration of onions, along with a gradual decrease in quercetin glucoside content. However, the quercetin aglycone increased simultaneously to 0.64 µmol g−1 fresh weight (FW) during the 10th week, while the fresh onions contained 0.06 µmol g−1 FW. The total sugar content decreased incessantly, while the total phenolics and flavonoids increased to 7080.67 ± 1248.20 µg gallic acid equivalents g−1 FW and 2340.10 ± 203.47 µg quercetin equivalents g−1 FW, respectively, during the 10th week. Under the aerobic condition, the total quercetin content was found to increase slowly but had a tendency to decrease during storage. The sugar content increased up to 6 weeks, followed by its gradual decrease. In addition, the total phenolics, flavonoids and antioxidant activity exhibited a decline during 1 month, with their highest content being observed during the 8th week.