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Twenty oenotannins from different botanical origins were studied in model wine solution (1 g/L, 12% ethanol, pH 3.5). An original device was created for measuring Oxidation–Reduction potential (<i>ORp</i>) of the solutions at 20 °C in strict anoxic condition by the electrochemical method of the platinum electrode zero-current potential. Reactivity against proteins and antioxidant properties were related to the chemical structure and, consequently, to the botanical origin of the oenotannins. The highest turbidity after BSA addition (ΔNTU > 1000) values were measured for the gallic hydrolysable tannins. The <i>ORp</i> versus standard hydrogen electrode ranged from 420 to 260 mV. The ellagitannins had the highest antioxidant power (<i>AP</i>%), followed by condensed tannins and gallotannins, highlighting a correlation with the phenolic profile. Based on these findings, two formulations were prepared as a blend of some of the tested oenotannins, with the ability to increase (MIX1) and decrease (MIX2) the <i>ORp</i> of the model wine.