Optimization of microwave-assisted extraction of antioxidants from potato peels

Potato processing by industries generates large volumes of potato peels which are a low-value by-product. They have been shown to contain significant levels of phenolic antioxidants with high antioxidant capacity. In the present study, effect of microwave-assisted extraction (MAE) on recovery of phenolic compounds from potato peels was investigated. Operational parameters of MAE were optimized using response surface methodology individually based on total phenolics, ascorbic acid, chlorogenic acid, caffeic acid, ferulic acid, DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity.;In the second part of the study effect of dielectric properties of solvent-water mixture used in MAE on extraction of antioxidants from potato peel was investigated. Linear regression models were obtained for establishing the effect of solvent concentration and temperature on dielectric properties of solvent-water mixture with and without introduction of potato peel. Solvent concentration significantly affected the dielectric properties of the solvent-water mixture and the total phenolics content of the extract obtained from the MAE process.;The independent extraction parameters for MAE such as extraction time, solvent concentration and microwave-power level were evaluated using a central composite design to access their effects and interactions on the extraction of phenolics from potato peels. Optimal predicted contents for total phenolics [3.94 mg g-1 dry weight (DW)] was obtained with a solvent concentration of 67.3% (v/v), an extraction time of 15 min and a microwave power level of 14.7% (102 W). Maximum ascorbic acid (1.44 mg g-1 DW), caffeic acid (1.33 mg g-1 DW) and ferulic acid (0.50 mg g-1 DW) contents were obtained with a solvent concentration of 100% (v/v), extraction time of 15 min, and power level of 10% (63W), while the maximum chlorogenic acid content (1.35 mg g-1DW) was obtained at a solvent concentration of 100% (v/v), an extraction time of 5 min, and a power level of 10% (63W). The radical scavenging activity of the extract was evaluated by using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and optimum antioxidant activity (74%) was obtained at a solvent concentration of 100% (v/v), an extraction time of 5 min, and a power level of 10% (63W). MAE was able to extract higher level of antioxidants compared to traditional methods of extraction in less time and with lower solvent consumption.