Optimization of the extraction of antioxidant phenolic compounds from grape pomace using response surface methodology

The extraction of phenolic compounds with antioxidant activity (AA) of winemaking by-products using response surface methodology and fractional factorial design was investigated. The effects of grape pomace from wine (GWP) and juice production (GJP), temperature, solvent type and time on the extraction of total phenolic compounds (TPC) and AA were evaluated. The TPC and AA varied from 17.91 to 35.10mg(GAE)g(-1) (gallic acid equivalent) and from 65.12 to 149.27 mu molTroloxg(-1) of pomace, respectively. For both by-products the optimization suggest that solvent acetone at 60 degrees C was the best condition. However, the best time for GJP and GWP were 15min and 45min, respectively. Gallic acid was the major phenolic compound identified by liquid chromatography in the GJP, followed by coumaric acid, ferulic acid, trans-resveratrol and caffeic acid. The content of anthocyanins for GWP and GJP varied from 640 to 780mgcyaniding(-1). The responses of the factorial design showed that the GJP had the highest content of TPC and AA when compared to the GWP. Despite superiority of the GJP, these finding supporting the utilization of both grape pomace in food industry due to their high amount of bioactive compounds.