Effect of Combining Pulsed Electric Fields with Maceration Time on Merlot Grapes in Protecting Caco-2 Cells from Oxidative Stress

The objective of this study was to investigate the effect of different maceration times (0, 2, 4, 8 and 14 days) after pulsed electric field (PEF) processing (1.5 kV/cm, either at 15 or 70 kJ/kg) on the release of anthocyanins from Merlot grapes (Vitis vinifera) and the bioprotective potentials of grape juice against H2O2-induced oxidative stress using human intestinal Caco-2 cell culture model. Cell viability, lactate dehydrogenase membrane leakage and nitric oxide production in Caco-2 cells were used as biomarkers to indicate general cellular health and integrity that ultimately represent the bioprotective potentials of grape juice. The results showed that PEF at 70 kJ/kg was the most effective in accelerating the release of anthocyanins from grape skin. Furthermore, the amount and the type of anthocyanins being released varied as a result of combined effect of PEF processing intensity and maceration time. Linear correlations between anthocyanins and the bioprotective capacity markers (R (2) = 0.4-0.8) were found. Compared to the untreated Merlot, PEF treatment either at 15 or 70 kJ/kg reduced the maceration time from 14 to 8 and 2 days, respectively, to achieve similar degree of bioprotective effect. This implies the possibility of using combined PEF and maceration time to tailor the profile of bioactive compounds with the same bioprotective potentials.