Optimization of Ultrasound-Assisted Extraction of Phenolic Compounds from Citrus sinensis L. Peels using Response Surface Methodology

The aim of this study was the optimization, by Response Surface Methodology (RSM), of Ultrasound Assisted Extraction (UAE) conditions for the recovery of phenolic compounds from C. sinensis peels with aqueous acetone at room temperature. A Central Composite Rotatable Design (CCD) was applied to determine the effects of extraction time (X1, 5-15 min), extraction amplitude (X2, 30-70%), and acetone concentration (X3, 30-70 %) on Total Phenolic Content (TPC expressed as Gallic Acid Equivalents GAE, according to the Folin’s assay) of the extract. The independent variables were coded at five levels and their actual values were selected based on the results of single factor experiments. Results showed that acetone concentration and extraction amplitude were the most significant (p<0.05) factors affecting the TPC yield. The optimum extraction conditions were found to be 8.33 min extraction time, 65.94 % extraction amplitude and 75.79 % acetone concentration. Under the optimized conditions, a TPC yield of 13.57±0.71 mgGAE/gdw was obtained which resulted very close to the predicted value of 14.16 mgGAE/gdw.