ULTRASOUND-ASSISTED EXTRACTION OF BIOACTIVE COMPOUNDS FROM GRAPE POMACE WITH A RECIRCULATION SYSTEM

The use of ultrasound-assisted extraction for bioactive compounds has been increasing as it offers an environmentally friendly and clean alternative to conventional extraction methods. This work aimed to evaluate the use of ultrasound combined with a recirculation system for extracting bioactive compounds from grape pomace produced during Syrah wine production. A ratio of 1:20 (solid:liquid) and a 50% ethanol solution were used in the extraction. An ultrasonic system with recirculation, equipped with a flow pump and an extraction cell with a sonotrode, was used. A central composite design (CCD) 22 optimization with factorial, central and axial points was developed. The independent variables included pump speed and ultrasound power, while the extraction time was set at 90 minutes. A total of eleven tests were performed. The concentration of phenolic compounds (CPC) was measured by Folin-Ciocalteu method, anthocyanin concentration (AC) was measured by differential pH method, and antioxidant activity (AA) was measured by ABTS and DPPH methods. These were evaluated as response variables. CPC values ranged from 854.78 ± 15.11 to 1403.7 ± 13.50 (mg gallic acid equivalents/100g), while AA values ranged from 40.39 ± 0.26 to 70.66 ± 1.65 and 29.25 ± 0.29 to 50.71 ± 0.51 μM trolox/g for ABTS and DPPH assay, respectively. Anthocyanin concentrations ranged from 14.87 ± 0.58 to 23.64 ± 0.16 mg (Cyanidin 3-glucoside)/100g. The mathematical models generated showed good coefficients of determination (R2 > 0.70) and a lack of fit (p > 0.05) relative to the pure error, which was not significant for the CPC and AA response variables. Only ultrasound power had a significant effect (p > 0.05) on the extraction process, so that as the power increases, the values of the response variables increase. The pump speed did not significantly influence (p < 0.05) the extraction process, not generating an increase or decrease in the values of the response variables. The results found in this work are promising, for example the values found for CPC are higher than some studies found in the literature that used ultrasound-assisted extraction. Therefore, ultrasound-assisted extraction with recirculation shows promise for recovering bioactive compounds from grape pomace.