The invention provides processes for treating commercial grade preservatives to remove the off-flavor and/or off-odor from the preservatives. The processes involve preparing a solution by dissolving the preservative in a suitable solvent, such as water or methanol or mixtures thereof. The preservative solution is then passed through a filter to separate and remove organic acid impurities from the preservative. The undesirable tastes and odors, principally caused by the organic acid impurities, are retained in the filter while the preservative passes through the filter. In one embodiment, the filter is a bed of anion exchange resin that reacts with and removes the organic acid impurities. In another embodiment, the filter contains a metal cation that converts the organic acid impurities into insoluble salts which remain in the filter. The solvent can be removed by evaporation after the preservative solution is passed through the filter.