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Shriveling. Rotting. Dousing with alcohol. Wineries will put their grapes through almost anything to satisfy a wine lover's sweet tooth.
Dessert wines, often rare and expensive, are unique wines and the most difficult to make; but when successful, they earn some of the highest ratings given by our editors. Enlisted to do a specific job in a specific situation, these luscious nectars are the special teams of the wine world. They accompany the dessert course, or even take its place and star on their own. Yet despite delivering high quality more often than not, dessert wines are generally misunderstood, underestimated or simply ignored.
Dessert wines come in many styles, and the techniques used to make them are almost as numerous. The three basic approaches described below are the most common, and unite dessert wines from diverse regions and grapes.
The technique used most frequently involves concentration. Increasing the sugar content of the grapes -- through drying them, allowing them to undergo desiccation on the vine by way of Botrytis cinerea ("noble rot") or removing the frozen water from the grapes after they have iced on the vine -- results in wines of high natural sweetness; when fermentation stops, residual sugar is left in the wines.
Adding neutral spirits (generally grape brandy) to arrest fermentation while residual sugar still remains in the juice is a second major method of producing sweet wines. Finally, a system of fractional blending known as a solera can add complexity to fortified wines, as the new harvest's wines are introduced into aging stocks of wine and the blends are moved through oak barrels.
Sweet wines made from dried grapes are classical in the true sense. Developed in ancient times around the Mediterranean basin, the sweet wines of ancient Greece, Phoenicia (modern-day Lebanon) and Rome were the cult Cabernets of their day. During the Middle Ages, sweet wines from the Mediterranean enjoyed success in more northerly European markets. Today, more than any other European country, Italy steadfastly clings to the tradition of making wines from grapes dried after picking.
The use of botrytized grapes probably first occurred in Hungary's Tokay region, when the harvest of 1650 was delayed due to skirmishes with the Turks. As the grapes hung on the vines into the humid autumn, noble rot attacked, desiccating the grapes and concentrating their sugars. The fermentation of grapes that were purposefully botrytized by delaying the harvest occured in Germany about a century later, and in Sauternes in the early 19th century. Botrytis may have played an integral part in sweet wines prior to these dates, without being fully understood or recognized.
Concentration through these natural methods was the major technique used to achieve sweet wines until the development of fortification in the 17th century. Port was initially a dry red, albeit at robust alcohol levels given the hot climate of the Douro. But at some point, winemakers discovered that a little brandy improved the wine and strengthened it for shipping. The consistent addition of grape spirit to Douro wine developed in the Port region in the mid-1700s. Brandy was also added, more haphazardly, to Sherry. In the latter half of the 18th century, a power struggle between growers and merchants ended with the merchants winning control of the aging and blending of Sherry stocks. As a result, fortification standards and distinct winemaking styles began to emerge.
Dried grape wines
Naturally sweet wines rely on the concentration of sugar in the grapes prior to fermentation. Dehydration can occur through botrytis (a fungus which attacks the skins causing grapes to shrivel), but if weather conditions don't induce botrytis, grapes left on the vine long enough will begin to shrivel anyway. Sauternes from France, beerenauslesen and trockenbeerenauslesen from Germany, and Hungarian Tokay are all made from naturally dried grapes, preferably via botrytis. The noble rot not only concentrates sugars, it adds honey, citrus and spice flavors, contributes viscosity and concentrates acidity. Drying grapes on mats after picking, a technique used in Italy for Recioto della Valpolicella and vin santo, achieves a similar effect.
Harvesting the shriveled grapes takes time and skill because it is necessary to make successive passes through the vines, sometimes picking berry by berry. The intensive labor required and the minute quantities of wine that result translate to high prices. The sugar content of the juice from the picked and pressed grapes is usually high enough (combined with the alcohol formed during fermentation) to inhibit yeast activity and ensure a significant amount of residual sweetness. Wines with residual sugar risk refermenting in the bottle; stabilization is provided by filtering the finished wine and adding sulfur dioxide.
In more northerly areas, such as Germany, France's Loire Valley and Alsace, and in the continental climate of Tokay in Hungary, high acidity characterizes the wines, balancing their intense sweetness. These are generally elegant rather than powerful, and relatively low in alcohol.
The Sauternes region in Bordeaux focuses almost entirely on the production of sweet wines. These tend to be somewhat high in alcohol, typically around 14 percent, and are therefore less sweet and also lower in acidity than are German beerenauslesen and trockenbeerenauslesen. Because the top estates ferment in barrels, often of new oak, the resultant flavors evoke vanilla and spice and tropical fruits such as pineapple, mango, apricot and citrus along with the honey and spice notes from botrytis.
For centuries, the Italians have relied on drying grapes after picking to make two of their unique sweet wines: vin santo and recioto della Valpolicella. From late autumn until the end of winter, grapes for these wines are laid out on straw mats in order to shrivel and concentrate their sugars. Recioto relies on the red grapes Corvina, Molinara and Rondinella, the same varieties blended for Valpolicella and Amarone. Corvina in particular is susceptible to botrytis, which adds complexity to the final wine, although some producers eschew any botrytis-affected grapes. After drying, the grapes are fermented in large, neutral oak casks until the desired level of residual sweetness is attained. Some younger winemakers are experimenting with smaller barrels and new oak. Vin santo is made in much the same way, commonly from Trebbiano and Malvasia grapes, but the barrels used tend to be smaller, rarely exceeding 300 liters in capacity.
Tokay is both a wine and a region, named after one of the towns near the vineyards of northeastern Hungary. When the Furmint and Hrslevelu«« grapes are 50 percent botrytized, a condition known locally as asz, the individual berries are harvested, and later used to sweeten dry wines. The asz berries are mixed to a paste in vessels known as puttonyos; the sweetness of the final wine is determined by the number of puttonyos added to the dry wine -- three, four, five or six. The wines are then stored in casks, where oxidation occurs, adding intense aromas. Tokay shows high levels of acidity and extract, buffering its varying levels of sweetness.
Fortification is the addition of a neutral spirit to arrest fermentation. The timing and strength of the alcohol addition determines the final level of sweetness in a fortified wine. Spirit may be added at or near the beginning of fermentation (France's vin doux naturel), during fermentation (Port) or after fermentation (Sherry).
Port hails from the Douro valley in Portugal and begins its life as grape must with a potential of roughly 13 percent alcohol. When about a third of the fermentation has occurred, grape spirit is added to kill the yeasts and stop the fermentation, increasing the alcohol to about 20 percent by volume. Because contact with the grape skins is brief, only two to three days, it is important to extract as much color and tannin as possible in that time period. Traditionally, the grapes were crushed by foot in shallow granite troughs called lagares. Today, most houses have replaced the lagar with autovinification tanks, although some still use lagares for their best-quality tawny Port and Vintage Port.
Port is aged either in wood or in bottle, with the aging vessel and length of time determining the Port's style. Ruby is the most straightforward, aged in wood or tank for two to three years, then bottled. Tawny Port spends at least six years aging in wooden casks, but often longer. The best quality components are used and blended to create wines that are then aged for a specified period of time, usually 10 or 20 years, but sometimes 30 or 40 years. The contact with oxygen softens the color to a burnished mahogany, hence the name tawny, and results in a rich, nutty character.
Vintage Port, made only in the best years, ages for two years in wood before being bottled. The slow maturation in bottle maintains the wine's deep ruby color and spicy, fruity character for the requisite 10 or 20 years it takes to soften the tannins. Whereas tawny Port is ready to drink once it is bottled, Vintage Port demands long bottle-aging before it reaches the peak of drinkability.
Like Port, Sherry, from the Andalusia region of Spain, comes in many styles. Unlike Port, however, it is fortified at the end of fermentation. Fino and oloroso are the two main categories, with each containing the possibility of several styles. Top quality sweet oloroso and cream Sherries are made by blending dried Pedro Ximnez grapes, which contain high levels of sugar, with dry oloroso.
Whatever the style, the best Sherries achieve their character through a system of fractional blending called a solera, in which a specific amount of Sherry is drawn off the oldest casks and is replaced systematically with sherry from the next oldest casks and so on throughout the entire system. Each year, a portion of the new harvest, known as a nursery, or criadera may be added. The concept is to nourish the older wines with the younger, while maintaining a mature character within the solera.
Liqueur Muscat and liqueur Tokay from Australia are hybrids in terms of the techniques used to make them. The grapes used are either Muscat or Muscadelle (the latter called Tokay in Australia). The grapes are partially dried naturally by the warm, dry climate before harvest, concentrating the sugars, then the wines are fortified during fermentation. The resulting wine is aged in a solera and is also subjected to heating during this period. The wines are thick and luscious, with flavors that range from dried fruits such as prune, fig and Muscat raisins to smokier overtones like tar, coffee and nuts.
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