The tannic nature of Cabernet Sauvignon is an important winemaking consideration. As the must is exposed to prolonged periods of maceration, more tannins are extracted from the skin and will be present in the resulting wine. If winemakers choose not to shorten the period of maceration, in favor of maximizing color and flavor concentrations, there are some methods that they can use to soften tannin levels. A common method is oak aging, which exposes the wine to gradual levels of oxidation that can mellow the harsh grape tannins as well as introduce softer "wood tannins". The choice of fining agents can also reduce tannins with gelatin and egg whites being positively-charged proteins that are naturally attracted to the negatively charged tannin molecules. These fining agents will bond with some of the tannins and be removed from the wine during filtration. One additional method is micro-oxygenation which mimics some of the gradual aeration that occurs with barrel aging, with the limited exposure to oxygen aiding in the polymerization of the tannins into larger molecules, which are perceived on the palate as being softer.