Abstract
Proanthocyanidins (PAs) and anthocyanins contents of four different red grape pomaces (GPs) from Morocco were analysed using chromatographic methods. The GP skin pigments characteristics were determined using spectroscopic methods while their antioxidant activities were determined using both spectroscopic methods as ABTS and DPPH radical cations, ferric reducing/antioxidant power (FRAP) and electrochemical technique: cyclic Voltammetry (CV). The PA of seeds extracts varied significantly among the types of GP and ranged from 56.1 +/- 0.3 mg g(-1) dry weight (DW) in Cot to 88.4 +/- 2.3 mg g(-1) DW in non-fermented Cabernet Sauvignon (CSNF). The skins of CSNF contained the highest levels of PAs (22.1 +/- 0.3 mg g(-1) DW). The PAs average degree of polymerization distribution ranged from 2 to 45 subunits for the skins and from 2 to 12 subunits for the seeds. The maximum anthocyanins amounts and antioxidant activities were measured in Cot skin extracts (32.8 mg g(-1) DW, DPPH: 0.23 mmol Trolox mg g(-1) DW; ABTS: 0.38 mmol Trolox mg g(-1) DW and CV: 1.73 x 10(-3)mA V) followed by Arinarnoa skin extracts which had the maximum corrected pigments (14.8 +/- 0.1) and color power (152.4 +/- 4.6 Unit color). The principal components analysis (PCA) of GP skins showed three different groups relevant to anthocyanins, PAs content, color and antioxidant properties.