White wine has existed for at least 4,000 years. White wines are often used as an apéritif before a meal, with dessert, or as a refreshing drink between meals. White wines are often considered more refreshing and lighter in both style and taste than the majority of their red wine counterparts. Due to their acidity, aroma, and ability to soften meat and deglaze cooking juices, white wines are often used in cooking.
The wide variety of white wines comes from the large number of varieties, methods of winemaking, and ratios of residual sugar. White wine is mainly from “white” grapes, which are green or yellow in color, such as the Chardonnay, Sauvignon Blanc and Riesling. Some white wine is also made from grapes with colored skin, provided that the obtained wort is not stained. Pinot noir, for example, is commonly used to produce champagne.
Among the many types of white wine, dry white wine is the most common. More or less aromatic and tangy, it is derived from the complete fermentation of the wort (the grape juice from the initial pressing process). Sweet wines, on the other hand, are produced by interrupting the fermentation before all the grape sugars are converted into alcohol; this is called Mutage or fortification. The methods of enriching wort with sugar are multiple: on-ripening on the vine, passerillage (straining), or the use of noble rot. Sparkling wines, which are mostly white, are wines where the carbon dioxide from the fermentation is kept dissolved in the wine and becomes gas when the bottle is opened.
Fermentation Process
White wine is fermented without skin contact. This means the skins are removed immediately after pressing. The color can be straw-yellow, yellow-green, or yellow-gold, the variety produced by the alcoholic fermentation of the non-colored pulp of grapes.
The wort, mentioned above, is placed in a tank to undergo fermentation. The majority of aromatic components (acetates of alcohol and ethyl esters of fatty acids) are synthesized by the yeast during fermentation of light juice below 18 °C.
Fermentation starts spontaneously under the action of the natural yeasts from the grapes. The winemaker can choose to use a commercially available active dry yeast. It can help to express the characteristics of a variety or a method of manufacture. For a dry white, wine fermentation continues until the sugar runs out. The wine is then usually decanted to eliminate the lees. When fermentation is done in barrels the temperature often exceeds 20 °C or even 25 °C.
After the end of fermentation, the wine may also have malolactic fermentation or FML. This second fermentation carried out by bacteria deacidifies the wine: it transforms the malic acid into lactic acid. This operation, which reduces the biting acidity of the wine, is not always desirable nor practiced. In southern areas for example, the acidity is carefully preserved to give the wine its liveliness for a refreshing aroma. During the fermentation of the grapes, varietal aromas are reduced in flavor of an increase in roundness and volume in the mouth of the wine during ageing in oak barrels.
For a sweet wine, fermentation is stopped before its end to keep some of the sugar: this is the Mutage (fortification). An addition of wine alcohol stops the fermentation. For sweeter dessert wines, fermentation stops spontaneously by excess sugar and alcohol: Alcohol is waste from the yeast and it is poisonous in large doses. In the case of sweet wines, FML is not done for sweet wines as the lactic bacteria preferentially degrades sugar which would give a lactic bite (sweet and sour wine). In addition, the balance of acidity and sugar in the wine supports vivacity.
Maturing the Wine
Maturing can be done in a vat. It takes little time to clarify and to prepare the packaging (bottling or Bag-In-Box) but this may be extended by maturing of lees. This type of maturing consists of regularly adding fine lees in suspension in the wine. The dead yeast is used for the fine lees which digests itself (autolysis) giving the wine volume and body to support the fruitiness. This operation is called Bâtonnage, or stirring, and is traditionally done with a stick to agitate the lees at the bottom of the barrel. This technique needs to be well controlled, however, otherwise the wine may take on a Goût de réduit (Reduced taste) due to the activity of reductase sulphite from the yeast. This operation can be done in vats, as in Muscadet, barrels as in Burgundy, and many chardonnays, or bottles as in champagne.
Maturing can also be done in barrels. The wine is put in barrels after fermentation but fermentation itself may also occur in the barrel. The barrel has a dual role: it flavors the wine giving it a scent of toast, butter, and vanilla but it also helps to mature it by providing a very small regular quantity of oxygen through the wooden walls. This oxygen helps to polymerize the components of the wine making it less aggressive and more balanced.
