Physicochemical Characterization of Potato Peel Flour (Solanum tuberosum L.) and Optimization of the Ultrasound-Assisted Extraction Process (UAE) of the Phenolic Compounds Using Response Surface Methodology

Abstract The objective of this research was to characterize potato peel flour, evaluate which solvent was best for extracting the phenolic compounds (PC), and optimize the ultrasound-assisted extraction by investigating the linear and squared effects and their interaction in recovering these compounds using an RCCD experimental design and response surface methodology associated with a desirability graph. The potato peel was donated by a local restaurant in the city of Goiânia (GO), and the results obtained for the physicochemical composition confirmed to those expected for this residue. Six solvents were used to extract the PC (ether, ethanol, water, methanol-acetone-water, 60% ethanol in water, and 10% ethanol in water), and the results showed that 10% ethanol in water gave the best results for total PC and antioxidant activity. A second RCCD experimental design was then used to obtain the ideal parameters for the ultrasound, and it was observed that, to obtain a fitted model that predicted the ideal extraction conditions with confidence, one must use three variables in the design: time, temperature, and the solid-liquid ratio. According to the response surface and desirability graphs, the ideal conditions to maximize the extraction of phenolic compounds from potato peels were: a time of 66.9 min, a temperature of 44.9 °C, and a solid-solvent ratio of 1:46.82 m/v. Thus, both the ultrasound and the experimental design helped maximize the recovery of PC from the potato peel flour.