Novel Technologies Assisted Extraction of Bioactive Compounds from Orange Peels Waste

The study evaluated the conventional extraction (CE), microwave-assisted extraction (MAE), ultrasound-assisted extraction (UAE), and pulsed electric fields-assisted extraction (PEFAE) of bioactive compounds from orange peel waste. The effect of extraction time (0–120 min), ethanol concentration (0, 50 & 80%), and temperature (25–70 °C) were investigated, while response surface methodology (RSM) was applied for each process optimization. MAE achieved the highest total phenolic content (TPC) (6.36 mg/g w.m.) under optimized conditions (50 kJ microwave energy, 50% ethanol, 60 min), representing approximately 12% higher recovery compared to CE (TPC: 5.29 mg/g w.m.; 50 °C, 55% EtOH, 80 min). UAE (90% amplitude, 66.4 W/kg) resulted in the highest flavonoid recovery (0.48 mg/g w.m.) using 50% ethanol at 50 °C for 90 min, while PEFAE (4 kV/cm, 1000 pulses) for 75 min extraction time exhibited the same TPC yield as CE and the highest antioxidant activity (1.12 mg/g w.m.) using only water at room temperature. RSM analysis confirmed that ethanol concentration and extraction time significantly affected extraction performance. These findings demonstrate the potential of green extraction technologies for sustainable valorization of citrus processing waste and recovery of high added-value compounds.