Physicochemical properties and antioxidant activity of Doshab (a traditional concentrated grape juice)

Doshab is a concentrated and shelf-life extended form of grape juice. The present study was outlined to investigate the physicochemical properties including pH, titratable acidity, soluble solids (˚Brix), and water activity (aw) as well as total phenolics and antioxidant activity of 19 Doshab samples from different production unites. The antioxidant activities of the samples were assessed by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity, β-Carotene bleaching and reducing power assays. The pH values and titratable acidity of Doshab samples were ranged from 5.3 to 6.2 and from 0.165 to 0.622 g per 100 g, respectively. In DPPH assay, radical scavenging activity of samples was ranged from 27.7% to 82.3%. Inhibition percentage (I %) of the linoleic acid oxidation was between 72.2% and 87.2%. Total phenolic contents of doshab samples were changed between 1.84 and 4.47 mg of gallic acid equivalent per g of the sample. There was no significant correlation between radical scavenging activity and total phenolic contents. A moderate correlation between I (%) and total phenolic content, as well as between reducing power and total phenolic content was obtained.