Determination of physicochemical properties and antioxidant activity profiles of fruit juice, marmalade, pickle, vinegar and sour vinegar produced from isabella scented grape (vitis labrusca L.)

This study aimed to comprehensively evaluate the physicochemical composition, bioactive properties, and antioxidant potential of five products derived from Isabella grape (Vitis labrusca L.). Among the products, marmalade exhibited the highest HMF content (2.37 mg/kg), followed by pickled grapes (1.84 mg/kg), while grape juice contained 0.59 mg/kg, and fresh grape, verjuice, and vinegar samples showed ≈0 mg/kg HMF. Soluble solid content (°Brix) ranged widely across samples, with marmalade containing 40.33%, whereas verjuice and pickled grapes contained 6.27% and 6.30%, respectively, and grape vinegar had 3.52%. Regarding phenolic compounds and antioxidant activity marmalade showed the highest levels with TPC 251.20 mg GAE/100 g, TFLK 132.73 mg QE/100 g, TAC 312.54 mg AA/100 g, FRAP 189.60 mg FeSO₄/100 g, and DPPH 74.49 mg AA/100 g. TPC values in other products were measured as 126.06 mg GAE/100 g in pickled grapes, 109.79 mg GAE/100 g in verjuice, 125.36 mg GAE/100 g in grape juice, 86.75 mg GAE/100 g in fresh grape, and 33.86 mg GAE/100 g in grape vinegar. As (PCA) results ; marmalade clustered strongly on the sugar–phenolic axis, pickled grapes on the acidity–color change axis, fresh grapes on the ascorbic acid axis, and grape vinegar on the low sugar–low antioxidant activity axis. Overall, the findings demonstrate that Isabella grape–based products exhibit distinct chemical characteristics depending on processing techniques, with marmalade and grape juice showing the highest functional potential.