EFFECTS OF FERMENTATION TIME AND EXTRACTION SOLVENT ON ANTIOXIDANT ACTIVITY AND TOTAL PHENOLIC AND FLAVONOID CONTENT OF PHENOLIC EXTRACT FROM ORANGE (Citrus reticulata) PEEL

The rise in consumption of oranges worldwide causes an increase in orange peel, which accounts for 30 - 35% of the orange's weight. Phenolic compounds found in orange peel are conjugated with the cell wall components. The utilization of solid-state fermentation by Aspergillus niger can release bound phenolic compounds from the cell wall, thereby hence increases phenolic compounds extraction. This study aims to determine the effects of the fermentation time of orange peel using A. niger and extraction solvents (methanol, ethanol, acetone) on the yield of orange peel extract, total phenolic content, total flavonoid content, antioxidant activity, and hesperidin content of orange peel extract. The results showed that all the parameters performed best after 3 days of fermentation. The extract yield, total phenolic content, and total flavonoid content were 34.1% (dry weight), 51.01 mg GAE/g extract, and 14.75 mg QE/g extract, respectively. Moreover, the highest antioxidant activity (IC50 value) and hesperidin content found in orange peel were 184.32 ppm and 27.47 mg/g (dry weight) using 80% ethanol. Furthermore, the utilization of deep eutectic solvent as a biodegradable and environmentally benign substitute for organic solvents was investigated, proving that the alternative mixture of choline chloride and ethylene glycol is competitive.