THE EFFECT OF EXTRACTION PARAMETERS ON ANTIOXIDANT ACTIVITY OF SUBCRITICAL WATER EXTRACTS OBTAINED FROM MANDARIN PEEL

Mandarin peel, which discarded as by-product at large amounts during fruit juice production, is a valuable source of antioxidant compounds in the food industry. The aim of this study was to investigate the effect of extraction temperature and static extraction time on antioxidant activity and phenolic compounds during subcritical water extraction. The antioxidant activity of subcritical water extracts were determined by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay as IC50, ferric ion reducing antioxidant power (FRAP) and total antioxidant potential assay using Cu(II) complex as an oxidant (CUPRAC). As the IC50 value of the subcritical water extracts obtained from mandarin peel decreased 40.8 times, FRAP and CUPRAC values increased 66.9 and 34.2 times with increasing extraction temperature from 50 to 180°C for 5 min, respectively. Besides, total phenolic content (TPC) of subcritical water extracts increased 4.9 and 5.0 times from 50 to 180°C for 5 and 15 min whereas, 9.6 and 9.9 times increase was obtained for total flavonoid content (TFC) in the subcritical water extracts, respectively.