Extraction of phenolic from Moroccan grape pomace: Optimization of decoction extraction of phenolic compounds using response surface methodology

Abstract

The present study focuses on the optimization of the parameters to extract phenolic products by decoction and the quantification of these compounds from grape pomace, using a central experimental design. The antioxidant activity of methanolic extracts from grape skin grown in Morocco was evaluated. The grapes variety is “Michael Paleiri”, it is a black variety with pips, and they are from the region of Benslimane. The total phenolic compounds contents were determined by the Folin-Ciocalteu method. The optimization suggested that extraction with methanol for 29 min, at 60°C were the best solutions for this combination of variables.The largest amount obtained was 1042.06 mg EGA/g DW. The antioxidant activity is carried out by the radical scavenging method 1,1-diphenyl-2-picryl hydrazyl (DPPH°) and the ferric iron reduction capacity (FRAP). The DDPH inhibition capacity reached 20.78%, compared with 15.22% of a BHT solution at 0.001 g/L. A significant relationship between antioxidant capacity and total phenolic content is evident (R2=0.994). These results demonstrate that methanol extracts from the waste from grapes grown in Morocco could be used as potential sources of natural extracts rich in phenolic compounds and endowed with significant antioxidant activity.