Optimization of Accelerated Solvent Extraction for Phenolic-Rich Extracts from Apple Peels and Comparison with Different Extraction Methods

Abstract This study had a primary objective of optimizing accelerated solvent extraction (ASE) conditions to obtain phenolic‑rich extracts from apple peels using response surface methodology. Conventional and ultrasound‑assisted extraction (UAE) methods were also compared with ASE under optimized-conditions. A central composite design was used to optimize ASE to maximize responses (the total phenolic (TPC) and flavonoid contents (TFC) and antioxidant activity (AA) of peel extracts), and the TFC, TPC, and AA of the extract obtained at optimum conditions (108.5 °C, 2.03% ethanol concentration, and 26 min extraction time) were 45.01 mg CE/L, 77.67 mg GAE/L, and 52.49 µmol TE/L, respectively. In the comparison of methods, while the extract of UAE showed the lowest TPC (1.80 mg GAE/g) ( p < 0.05), the TPCs of ASE under optimized conditions and conventional extracts were 13.82 and 14.22 mg GAE/g ( p > 0.05), respectively. AA values of extracts were comparable for ASE (8.95 µmol TE/g) and UAE (8.72 µmol TE/g), both higher than conventional extraction (4.64 µmol TE/g). In contrast, the highest TFC was obtained from the UAE extract (10.68 mg CE/g) ( p < 0.05), followed by ASE (6.58 mg CE/g) and conventional extraction (5.64 mg CE/g). Overall, ASE was found effective for extracting compounds from apple peel, producing phenolic-rich extracts with superior or comparable bioactive properties under optimized-conditions compared to other methods.