Comparison of Different Extraction Methods on the Recovery Efficiencies of Valuable Components from Orange Peels

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Supercritical-CO2 extraction, Soxhlet extraction, and ultrasound-assisted extraction methods were conducted in this study to recover valuable components, specifically phenolic antioxidant compounds, from orange peels. Basic operating parameters such as temperature and pressure, which affect the extraction efficiency of phenolic substances in orange peel with supercritical-CO2, were designed using the central composite design methodology. In the Soxhlet and ultrasound-assisted extraction methods, 2-hour extraction processes were carried out using ethanol at different concentrations (50%, 80% and 100%) as a solvent. Yield comparison was made by performing total phenolic content, antioxidant activity and total flavonoid content analyses in the extracts. The total phenolic content (TPC) in the extracts was determined to be 5034 mg GAE/L for supercritical-CO2 extraction at 61.5°C and 20 MPa. In comparison, Soxhlet extraction yielded a TPC of 1728 mg GAE/L, while the ultrasound-assisted extraction method resulted in a TPC of 4056 mg GAE/L. It was determined that the optimum operating parameters of supercritical-CO2 extraction were 60°C and 26.4 MPa in case all the responses were maximized. The best phenolic recovery was obtained at 100% ethanol in Soxhlet extraction and 80% ethanol in ultrasound-assisted extraction. Although supercritical-CO2 extraction is an environmentally friendly application, the recovery rate of valuable components from raw materials is lower than in Soxhlet extraction and ultrasound-assisted extraction. However, since the volume of the extracts obtained from the supercritical-CO2 extraction is small, the ratio of phenolic compounds is higher.