Tuesday, November 4, 2008

Cabernet Sauvignon

Cabernet Sauvignon is one of the world's most widely recognized red wine grape varieties. It is grown in nearly every major wine producing country among a diverse spectrum of climates from Canada's Okanagan Valley to Lebanon's Beqaa Valley. Cabernet Sauvignon became internationally recognized through its prominence in Bordeaux wines where it is often blended with Merlot and Cabernet franc. From France, the grape spread across Europe and to the New World where it found new homes in places like California's Napa Valley, Australia's Coonawarra region and Chile's Maipo Valley. For most of the 20th century, it was the world's most widely planted premium red wine grape until it was surpassed by Merlot in the 1990s.

Despite its prominence in the industry, the grape is a relatively new variety, the product of a chance crossing between Cabernet franc and Sauvignon blanc during the 17th century in southwestern France. Its popularity is often attributed to its ease of cultivation - the grapes have thick skins and the vines are hardy and resistant to rot and frost - and to its consistent presentation of structure and flavours which express the typical character ("typicity") of the variety. Familiarity and ease of pronunciation have helped to sell Cabernet Sauvignon wines to consumers, even when from unfamiliar wine regions. Its widespread popularity has also contributed to criticism of the grape as a "colonizer" that takes over wine regions at the expense of native grape varieties.

For many years, the origin of Cabernet Sauvignon was not clearly understood and many myths and conjunctures surrounded it. The word "Sauvignon" is believed to be derived from the French sauvage meaning "wild" and to refer to the grape being a wild Vitis vinifera vine native to France. Until recently the grape was rumoured to have ancient origins, perhaps even being the Biturica grape used to make ancient Roman wine and referenced by Pliny the Elder. This belief was widely held in the 18th century, when the grape was also known as Petite Vidure or Bidure, apparently a corruption of Biturica. There was also belief that Vidure was a reference to the hard wood (French vigne dure) of the vine, with a possible relationship to Carménère which was once known as Grand Vidure. Other theories were that the grapevine originated in the Rioja region of Spain.[3]

While the period when the name Cabernet Sauvignon became more prevalent over Petite Vidure is not certain, records indicate that the grape was a popular Bordeaux planting in the 18th century Médoc region. The first estates known to have actively grown the variety (and the likely source of Cabernet vines for other estates) were Château Mouton and Château d'Armailhac in the Pauillac.

The grape's true origins were discovered in the late 1990s with the use of DNA typing at the UC Davis Department of Viticulture and Enology, by a team lead by Dr. Carole Meredith. The DNA evidence determined that Cabernet Sauvignon was the offspring of Cabernet franc and Sauvignon blanc and was most likely a chance crossing that occurred in the 17th century. Prior to this discovery, this origin had been suspected from the similarity of the grapes' names and the fact that Cabernet Sauvignon shares similar aromas with both grapes--such as the black currant and pencil box aromas of Cabernet franc and the grassiness of Sauvignon blanc.

While Cabernet Sauvignon can grow in a variety of climates, its suitability as a varietal wine or as a blend component is strongly influenced by the warmth of the climate. The vine is one of the last major grape varieties to bud and ripen (typically 1-2 weeks after Merlot and Cabernet franc) and the climate of the growing season affects how early the grapes will be harvested. Many wine regions in California give the vine an abundance of sunshine with few problems in ripening fully, which increases the likelihood of producing varietal Cabernet wines. In regions like Bordeaux, under the threat of incremental harvest season weather, Cabernet Sauvignon is often harvested a little earlier than ideal and is then blended with other grapes to fill in the gaps. As global warming has increased the number of warm vintage years, the possibility of creating varietal Cabernet in Bordeaux has also increased, making the decision to blend based more on ideology and tradition. In some regions, climate will be more important than soil. In regions that are too cool, there is a potential for more herbaceous and green bell pepper flavours from less than ideally ripened grapes. In regions where the grape is exposed to excess warmth and over-ripening, there is a propensity for the wine to develop flavours of cooked or stewed blackcurrants.

The Cabernet grape variety has thrived in a variety of vineyard soil types, making the consideration of soil less of concern particularly for New World winemakers. In Bordeaux, the soil aspect of terroir was historically an important consideration in determining which of the major Bordeaux grape varieties where planted. While Merlot seemed to thrive in clay and limestone based soils (such as those of the Right Bank regions of the Gironde estuary), Cabernet Sauvignon seemed to perform better in the gravel based soil of the Médoc region on the Left Bank. The gravel soils offered the benefit of being well drained while absorbing and radiating heat to the vines, aiding ripening. Clay and limestone based soils are often cooler, allowing less heat to reach the vines, delaying ripening. In regions where the climate is warmer, there is more emphasis on soil that is less fertile, which promotes less vigor in the vine which can keep yields low. In the Napa Valley wine regions of Oakville and Rutherford, the soil is more alluvial and dusty. Rutherford Cabernet Sauvignon has been often quoted as giving a sense of terroir with a taste of "Rutherford dust". In the South Australian wine region of Coonawarra, Cabernet Sauvignon has produced vastly different results from grapes vines planted in the region's terra rosa soil-so much so that the red soil is considered the "boundary" of the wine region, with some controversy from wine growers with Cabernet Sauvignon planted on red soil.

In addition to ripeness levels, the harvest yields can also have a strong influence in the resulting quality and flavors of Cabernet Sauvignon wine. The vine itself is prone to vigorous yields, particularly when planted on the vigorous SO4 rootstock. Excessive yields can result in less concentrated and flavorful wine with flavors more on the green or herbaceous side. In the 1970s, a particular clone of Cabernet Sauvignon that was engineered to be virus free was noted for its very high yields-causing many quality conscious producers to replant their vineyards in the late 20th century with different clonal varieties. To reduce yields, producers can plant the vines on less vigorous rootstock and also practice green harvesting with aggressive pruning of grape clusters soon after veraison.

In general, Cabernet Sauvignon has good resistance to most grape diseases, powdery mildew being the most noted exception. It is, however, susceptible to the vine diseases Eutypella scoparia and excoriose.

The "green bell pepper" flavor

There are a couple of noted Cabernet Sauvignon flavors that are intimately tied to viticultural and climate influences. The most widely recognized is the herbaceous or green bell pepper flavor caused by pyrazines, which are more prevalent in under-ripened grapes. Pyrazine compounds are present in all Cabernet Sauvignon grapes and are gradually destroyed by sunlight as the grape continues to ripen. To the human palate this compound is detectable in wines with pyrazine levels as low as 2 nanograms (ng) per liter. At the time of veraison, when the grapes first start to fully ripen, there is the equivalent pyrazine level of 30 ng/l. In cooler climates, it is difficult to get Cabernet Sauvignon grapes to ripen fully to the point where pyrazine is not detected. The green bell flavor is not considered a wine fault but it may not be desirable to all consumers' tastes. The California wine region of Monterey was noted in the late 20th century for its very vegetal Cabernet Sauvignon with pronounced green pepper flavor, earning the nickname of "Monterey veggies". In addition to its cool climate, Monterey is also prone to being very windy, which can have the effect of shutting down the grape vines and further inhibiting ripeness.

Two other well known Cabernet Sauvignon flavors are mint and eucalyptus. Mint flavors are often associated with wine regions that are warm enough to have low pyrazine levels but are still generally cool, such as Australia's Coonawarra region and some areas of Washington State. There is some belief that soil could also be a contributor to the minty notes, since the flavor also appears in some wines from the Pauillac region but not from similar climate of Margaux. Resinous Eucalyptus flavors tend to appear in regions that are habitats for the eucalyptus tree, such as California's Napa and Sonoma valleys and parts of Australia, but there has been no evidence to conclusively prove a direct link between proximity of eucalyptus trees and the presence of that flavor in the wine.
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