The effects of alcohol fermentation on the extraction of antioxidant compounds and flavonoids of pomelo peel

In this study, four kinds of fermented liquids with the different alcohol concentrations (1.5%, 4.5%, 7.4% and 9.4%, respectively) were prepared by pomelo peels. The flavonoid contents and antioxidant activities of the pomelo fermented liquids (PFLs) at three different fermentation stages, including the initial pulps (IP) before fermentation, after the main fermentation (MF) and after the post-fermentation (PF) were investigated. The results indicated that the flavonoid contents in PFLs were increased after fermentation. The PFLs had antioxidant abilities and their antioxidant abilities were consistent with the changes of flavonoids during the fermentation. Five flavonoids (Vicenin-2, Naringin 4′-glucoside, Naringin, Melitidin, and Acetyl naringin) were identified from PFLs at the fermentation stage of IP, while four flavonoids (Vicenin-2, Naringin, Melitidin, and Acetyl naringin) were identified from PFLs at the fermentation stages of MF and PF.