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Maceration: This process, used primarily in making red wine, involves steeping grape skins and solids in wine after fermentation, when alcohol acts as a solvent to extract color, tannins and aroma from the skins (aided by heat, the amount of skin contact and time). Cold maceration (steeping when the must is not heated), takes place before fermentation.
Made and Bottled By: On U.S. labels, this indicates only that the winery crushed, fermented and bottled a minimum of 10 percent of the wine in the bottle.
Magnum: An oversized bottle that holds 1.5 liters.
Malic Acid: A sharp, tart acid found in grapes as well as in green apples. Less-ripe grapes or grapes grown in cooler climates can contain high levels of malic acid; the resulting wines often contain aromas and flavors reminiscent of green apples. It is converted to smoother lactic acid during malolactic fermentation.
Malolactic Fermentation (ML): A bacterial fermentation occurring in most wines, this natural process converts sharper malic acid (found in green apples) into softer lactic acid (found in milk). Total acidity is reduced; the wines become softer, rounder and more complex. In addition, malolactic fermentation stabilizes wines by preventing an undesirable fermentation in the bottle. Often called the secondary fermentation. Frequently associated with big, rich, buttery Chardonnay, malolactic fermentation is prevented when fresher, crisper styles are desired.
Manzanilla: Manzanilla is a category of fino Sherry made only in Sanlucar de Barrameda. It is lighter and drier than most finos.
Masculine: Describes wines with firmness, power and strength.
Mature: The stage at which the wine will not gain any additional complexity with further bottle aging and is ready to drink. Also describes grapes when they are fully ripe.
Meaty: Describes red wines that show plenty of concentration and a chewy quality. They may even have an aroma of cooked meat.
Mercaptans: Also known chemically as thiols, mercaptans are organosulfur compounds that emit unpleasant, skunky aromas of rubber, sulfur or garlic. Mercaptans are often encountered in wines suffering from reduction (in which case exposure to oxygen may alleviate the flaw) as well as in very old white wines.
Meritage: An invented term, used by California wineries, for Bordeaux-style red and white blended wines. Combines "merit" with "heritage." The term arose out of the need to name wines that didn't meet minimal labeling requirements for varietals (i.e., 75 percent of the named grape variety). For reds, the grapes allowed are Cabernet Sauvignon, Merlot, Cabernet Franc, Petit Verdot and Malbec; for whites, Sauvignon Blanc and Sémillon. Joseph Phelps Insignia and Flora Springs Trilogy are examples of wines whose blends vary each year, with no one grape dominating.
Méthode Champenoise: The labor-intensive and costly process whereby wine undergoes a secondary fermentation inside the bottle, creating bubbles. All Champagne and most high-quality sparkling wine is made by this process. Also known as méthode traditionnelle.
Méthode Traditionnelle: See Méthode Champenoise.
Microoxygenation: This technique, used almost exclusively on red wines, allows winemakers to control the amount of oxygen that wines in tank are exposed to. The apparatus involves chambers connected by tubes and valves to an oxygen tank. Small, measured amounts of oxygen are allowed to pass through the wine via a porous stone or ceramic plate at or near the base of the tank. The benefits of this type of oxygen exposure include prevention of oxidation and reduction as well as promotion of healthy yeast cultures, which prevent stuck fermentations. Microoxygenation is also believed to soften tannins and, in conjunction with the use of oak chips, is frequently practiced as an alternative to oak barrel aging.
Millerandage: Also known as "hens and chicks," millerandage is an irregular fruit set in which the berries on a grape cluster are not uniform in size, with some achieving full size while others remain tiny and seedless.
Mouthfeel: Describes the sensation of wine in the mouth. Most descriptors are related to texture, for example: silky, smooth, velvety and rough. Mouthfeel is influenced by wine components, as acidity can be sharp, alcohol can be hot, tannins can be rough and sugar can be thick or cloying.
Murky: More than deeply colored; lacking brightness, turbid and sometimes a bit swampy. Mainly a fault of red wines.
Must: The unfermented juice of grapes extracted by crushing or pressing; grape juice in the cask or vat before it is converted into wine.
Must Weight: Measurement of the sugar content in grape must, or unfermented grape juice, which indicates the potential alcohol of the juice were all of the sugar to be converted to alcohol during fermentation. Like Brix, Baumé and Oechsle, must weight is more accurately a measurement of the must's density or specific gravity.
Musty: Having an off-putting moldy or mildewy smell. The result of a wine being made from moldy grapes, stored in improperly cleaned tanks and barrels, or contaminated by a poor cork.
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