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 ageing, 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. Affinity for oak One of the most noted traits of Cabernet Sauvignon is its affinity for oak, either during fermentation or in barrel aging. In addition to having a softening effect on the grape's naturally high tannins, the unique wood flavours of vanilla and baking spice complement the natural grape flavours of blackcurrant and tobacco. The particular success of Cabernet-based Bordeaux blends in the 225 litres (59 gallons) barrique significantly influenced that barrel size one of the most popular worldwide. In winemaking, the decision for the degree of oak influence (as well as which type of oak) will strongly impact the resulting wine. American oak, particularly from new barrels, imparts more robust oak flavours less subtle than those imparted by French oak. Even within the American oak family, the location of the oak source also plays a role, with oak from the state of Oregon having a more pronounced influence on Cabernet Sauvignon than oak from Missouri, Pennsylvania and Virginia. Winemakers often use a variety of oak barrels from different locations and of different ages and blend the wine as if they are blending different grape varieties. Winemakers can also control the influence of oak by using alternatives to the standard barrique barrels. Larger barrels have a smaller wood-to-wine ratio and, therefore, less pronounced oak flavours. Winemakers in Italy and Portugal sometimes use barrels made from other wood types such as chestnut and redwood. Another method that winemakers consider is tea bagging with oak chips or adding oak planks to the wines while fermenting or ageing it in stainless steel tanks. While these methods are less costly than oak barrels, they create more pronounced oak flavours, which tend not to mellow or integrate with the rest of the wine's components, nor do they provide the gradual oxidation benefit of barrel ageing. Wine regions Bordeaux The Bordeaux wine region is intimately connected with Cabernet Sauvignon, even though wine is rarely made without the blended component of