Ultrasound extraction of bioactive compounds from Citrus reticulata peel using electrolyzed water

The aim of this study was to evaluate the use of acid electrolyzed water, basic electrolyzed water, and slightly acidic electrolyzed water (AEW, BEW, and SAEW, respectively) as solvents in ultrasound (US) to extract bioactive compounds from Citrus reticulata. The influence of the intensity (17–85 W/cm2) and pulse cycles (0.5–1.0 dimensionless) was investigated in relation to the extraction of total phenolics (TP), total flavonoids (TF), and antioxidant activity (FRAP). The extract obtained with US + SAEW presented the highest values for TP (4,324.32 mg GAE.100/g of tangerine peel) and FRAP (663.69 µmol TEAC.100/g of tangerine peel). The highest TF content was found for US + AEW (691.76 mg EQ.100/g of tangerine peel). Response surface methodology showed that higher US intensities improved the extraction of phenolic compounds. Regarding the flavonoid compounds, the highest extractions were obtained at the central points (intensity (51 W/cm2) and cycle (0.75). The results showed that US and electrolyzed water successfully extracted bioactive compounds from tangerine peel; the processing time was also reduced by around 87.5%. These results were higher than those in the literature regarding conventional extraction techniques. Practical applications The combination of unconventional techniques (ultrasound and electrolyzed water as solvent) is characterized as a new methodology for the extraction of bioactive compounds from tangerine peel. This technique is environmental friendly due to the use of fruit residues, as well as the absence of organic solvents, and lower levels of energy use. The extract provided a higher content of total phenolics and total flavonoids than conventional methods. The extract can be incorporated into foods to provide nutritional quality and antioxidant properties. This technique is easily incorporated at the industrial level and is low cost after the purchase of the relevant equipment.