Maceration: a key step in the winemaking process - particularly for red wine - during which the grape skins and juice (must) remain in contact, allowing for the extraction of color, aroma and ultimately tannin. The total length of the maceration process can vary from as little as a couple of hours (for whites and roses) to a couple of days (for lighter reds) or even over a month (known as extended maceration). In white wine-making the process is generally bypassed, so as to avoid the extraction of undesirable tannins.
Macroclimate: an undefined term used to describe the climate of a large geographical area such as a large region, a country or even an entire continent. Compare with 'mesoclimate' and 'microclimate' (see below).
Malolactic fermentation: a winemaking process to reduce the harshness of a wine and impart added mouthfeel (see below), known colloquially as 'malo'. The process involves the conversion of strong malic acid to softer lactic acid through the actions of lactic acid bacteria.
Marc: the dry residue of seeds, stalks and skins left behind after grape pressing. Marc is commonly used to produce eau-de-vie, such as 'Marc de Champagne', but is also a convenient form of fertilizer.
Maritime climate: A maritime climate affects regions typically located near oceans or other large bodies of water, which act as temperature moderators.
Mediterranean climate: a climatic condition in which the summers are normally dry, warm to hot and sunny, and the winters are mild. The reliable growing season, characterized by plenty of sunshine and heat, makes it a climate prized by grape-growers. The lack of humidity also helps prevent against fungal diseases. On the other hand, the vines can be stressed due to a lack of moisture and the must weight (see below) can also increase to precarious levels in the heat.
Mesoclimate: the climate of a particular grape-growing site, which can be as broad as a village (commune in French) or clusters of vineyards on a slope, or as specific as a single small vineyard. It is an intermediate scale between macroclimate (see above) and 'microclimate'.
Metayage: a French term denoting a 'vines for wine' sharecropping system historically used in several European wine regions, most notably in Burgundy. A land owner would rent his vineyard out to a vine-grower, taking a percentage of the annual harvest (either as grapes or wine) as payment.
Méthode traditionnelle: the 'traditional method' used to produce sparkling wines. The term has been particularly useful since 1994, when the European Union ruled that the synonymous Methode Champenoise (Champagne method) could be used officially only in the Champagne region. Other analogous terms include 'Méthode Classique', 'Classic Method' and 'Metodo Classico'. The process is defined by a secondary in-bottle fermentation, induced by adding a liqueur de tirage (a mixture of wine, sugar and yeast). The carbon dioxide produced by this secondary fermentation is trapped inside the bottle, giving the wine its sparkle. Other stages in the methode traditionelle include riddling or rémuage (in which the upturned bottle is regularly turned, to bring the dead yeast cells into the bottle neck) and disgorgement (in which these cells are removed). The final step before corking is dosage, in which the bottle is topped up with a mix of base wine and sugar (liqueur d'expédition).
Methoxypyrazines: volatile aroma compounds which cause 'green' or herbaceous flavors in wine. Often found in wines made from under-ripe grapes, particularly those grown in cooler climates. While high levels of methoxypyrazines are considered a negative trait, the varietal character of some grape varieties (particularly Cabernet Sauvignon, Carmenere and Sauvignon Blanc) depend on the presence of low-level methoxypyrazines. Some species of ladybug (which sometimes make their way in among harvested grapes) have been found to emit methoxypyrazines.
Microclimate: refers to the climatic conditions surrounding a very small area. In the vineyard it refers to the area within and in immediate vicinity of the vines, around the vine canopy, the grape bunches, leaves and shoots, and well as soil temperature, humidity, dew, frost and so on. It is an extremely important tool which informs various vineyard practices aimed at matching a vine's performance to local conditions.
Micro-oxygenation: (microbullage in French) a winemaking technique that introduces small, precise amounts of oxygen into wine, particularly useful for softening red wines with aggressive tannins. This controlled amount of oxygen promotes polymerization (binding) of these harsh phenolics, thereby making them feel less astringent in the mouth. Micro-oxygenation also helps with color stabilization in red wines, by assisting in the polymerization of anthocyanins. The technique can also be used to encourage healthy yeast growth during fermentation.
Mildew: a vine-damaging fungal disease, the most significant forms of which are peronospora (downy mildew) and oidium (powdery mildew).
Monopole: a term predominantly used in Burgundy for a single vineyard, or a defined vineyard area responsible for the production of a single label from a particular producer.
Mouthfeel: a term used to denote the sensations in the mouth produced by food and drink. In wine-tasting are numerous terms that are often used when discussing mouthfeel, such as 'smooth', 'light', 'heavy', 'dense', 'viscous', 'big' and 'grainy'.
Must: freshly pressed grape juice containing the skins, seeds and stems of the berries.
Must weight: a measure of grape ripeness, based on the levels of fermentable sugars which will decide the potential alcohol of a wine. Various units are used to measure must weight. The most commonly used are Brix, Baume and Oeschle are the most common.
Mutage: a winemaking process to artificially stop or 'mute' the alcoholic fermentation of grape juice (must), resulting in a wine with high levels of residual grape sugar. It involves the creation of an environment inhospitable to yeast, either by the addition of grape spirit or sulfur dioxide. Mutage is a standard procedure for making vin doux naturel and fortified wines.
Négociant: a French term for the wine merchants (companies) who buy grapes, must, grape juice and wine at various stages of completion and maturation, for vinification, maturation and blending. The results will be bottled and solder under the negociant's own label.
New World: a generic term for all wine regions outside the Old World. Although the New World has adopted many techniques from the Old World, it has also been responsible for many innovations and scientific advancements in viticulture and winemaking. Overall, the wine laws in the New World are more lenient and flexible than their Old World counterparts.