01–1000 mg/L (R2 = 0.99) and expressed as mg of gallic acid equivalents (GAE)/L of grape juice. The analysis was performed in triplicate for each juice. selleck chemical The total monomeric anthocyanins content
was determined by the pH-differential method (Giusti & Wrolstad, 2001). Absorbance was read on the wavelength range of 420–520 nm of maximum absorption of monomers and at 700 nm. All grape juices were analyzed in triplicate and results were expressed as mg/L of malvidin-3,5-diglycoside as the main monomeric anthocyanin in V. labrusca L. (molar absorptivity of 37.000 L/cm/mol and molecular mass of 724.5 g/mol). The in vitro antioxidant capacity of juice samples was determined using the DPPH radical scavenging method ( Brand-Williams, Cuvelier, & Berset, 1995) and the ABTS radical scavenging method according to Re et al. (1999). The free radical scavenging activity was measured through
the rate of decay in absorbance at 517 nm for the DPPH radical and 754 nm BIBW2992 clinical trial for ABTS radical ( Kim, Guo, & Packer, 2002; Re et al., 1999). The analyses were carried out in triplicate and results were expressed as Trolox equivalents (mmol TE/L). The elemental analysis of grape juices was conduced according to Tormen et al. (2011). An aliquot of 500 μL of grape juice was diluted to 10 mL with 0.14 mol/L nitric acid and directly analyzed by ICP-MS. The external calibration was accomplished against aqueous standards in 0.14 mol/L nitric acid. To correct non-spectral interferences, 10 μg/L Rh was used as internal standard for all determinations. The method accuracy was assessed by analysis of two certified samples from NIST (Gaithersburg, USA) and recovery tests directly in dilute grape juices. The certified samples used correspond to water (SRM 1643e) and bovine liver sample (SRM 1577b).
Statistical analysis was performed using the Statistica software package version 7.0 (StatSoft Inc., Tulsa, USA). Data were subjected to analysis of variance and the significance cAMP inhibitor was assessed using the Tukey HSD test. The Pearson’s correlation test was used to evaluate the correlation between grape seed addition and the total phenolic content, antioxidant capacity, and mineral content of the juices. All analyses were performed in triplicate and the results expressed as mean ± standard deviation (SD). As classic parameters of grape juice quality, the pH and total soluble solids content were determined for all the varietal juices, and the results showed no significant difference between the control juices and the juices obtained from berries macerated with seeds. The soluble solids content in samples ranged from 3.9 to 4.4 °Brix in Bordo juices, 4.3 to 4.9 °Brix in Concord juices, and 4.3 to 4.8 °Brix in Isabel juices. The corresponding pH values were 3.43–3.46, 3.44–3.46 and 3.39–3.41, respectively. The total phenolic content, total monomeric anthocyanins and the in vitro antioxidant capacity of the three varietal grape juices are summarized in Table 2.