Astringency, the sensation of dryness or puckering in the mouth caused by full-bodied wine, is widely attributed to interactions between condensed tannins, or flavan-3-ol polymers, and salivary lubricating proteins. The current methods for chemically characterizing astringency correlate astringency with tannin concentration or with tannin-protein aggregate formation. Neither approach accounts for interactions between tannins and wine macromolecules such as polysaccharides, which have been shown to mediate the astringency of tannins. In this study, astringency is correlated with diffusion coefficient. Binding between macromolecules and tannins is expected to significantly alter diffusion coefficient. Diffusion coefficients for flavan-3-ol monomers, free and bound to bovine serum albumin (BSA), were measured using chronoamperometry. Measurements were made with a macro-electrode to establish that the difference between free and bound tannin diffusion coefficient can be resolved with chronoamperometry. The use of a microelectrode was explored as a concentration-independent approach, which is essential for application of this method in wine.