Wine Production



MACERATION. The soaking of grape solids in their juice. This can take the form of cold soak pre-fermentation or, in the case of red wines, post-fermentation. Maceration will help extract flavors and, for red wines, color and tannins.

MADERIZATION. A rather confusing term probably better dropped in favor of oxidation or/and heated. It derives from the chemical and sensory characters of Madeira-type wines that are both oxidized and baked. It is not related to wood-extract flavors as Spanish speakers might assume.

MALIC ACID. A strong tasting acid in wine reminiscent of the flavor of green apples. The amount of malic acid in grapes is gradually reduced during the ripening process while the grapes are on the vine and can be further reduced during winemaking by fermentation and malolactic fermentation.

MALOLACTIC FERMENTATION (MLF). A fermentation that may take place after (or occasionally during) the alcoholic fermentation, by which bacteria convert harsh malic acid into soft lactic acid. Almost without exception, it is desirable in red wines, but in white wines the winemaker may encourage or block it, depending upon the style required.

MARC. Skins, stalks and pips left after pressing grapes. May be distilled into brandy.

MATURATION. The time-related improvement of wines before bottling, especially bulk maturation in oak containers. After maturation appropriate to the type and style, a wine is considered mature, ready, and ripe to bottle.

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 Semillon.

MICROBIOLOGY. The science of microscopic life forms.

MICROORGANISM. Organism of microscopic size: yeast, bacterium, virus.

MICRO-OXYGENATION. Controlled exposure of wine to small amounts of oxygen to encourage polymerization of phenols.

MINERALS. Naturally occurring substances containing important salts of metals.

MOG. A winemaking abbreviation for Material Other than Grapes. Usually refers to debris like leaves, dirt, and stems that can be unintentionally harvested with the grapes.

MOLECULE. The smallest particle of a substance that retains the characteristic properties of the substance.

MUST. Unfermented grape juice, seeds, skins, and pulp.

MUST ADJUSTMENT. The addition of various substances before fermentation to ensure the desired chemical balance. For example, this may include additions of tartaric acid (acidification), often practiced in hot climates. Deacidification may be required in cool climates.

MUST CONCENTRATORS. Machines used to remove water from the juice of grapes. They can prove valuable following a wet vintage.

MUST ENRICHMENT. Process before or in the early stages of fermentation whereby the sugar content of the must is increased to raise the alcohol level of the wine. It may be undertaken in cool climates where grapes struggle to ripen. This is strictly controlled by law in the European Union. See also Chaptalization.

MUST WEIGHT. Measurement of density of must. In practice, this indicates the sugar levels contained in crushed grapes or juice. See also Baum�, Brix, Oechsle.

MUTAGE. The addition of alcohol to stop fermentation�used in the making of sweet fortified wines.