Glossary of Winemaking Terms - M

M

Maceration

The contact of grape skins with the must during fermentation, extracting phenolic compounds including tannins, anthocyanins, and aroma. See also cuvaison.

Madeirized

A wine showing Madeira-like flavor, generally evidence of oxidation. Sometimes used to describe white wine that has been kept long past its prime.

Maillard reactions

The complex chemical reaction between amino acids and sugar in the wine or grapes. During the raisining process of grapes, such as in the production of straw wine, the Maillard reaction process play a vital role in concentrating the flavors of the grapes. During sparkling wine production, the amino acids created during the autolysis process reacts with the residual sugar of the wine to create a series of aromas and flavors associated with premium quality Champagne.

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

Also known as malo or MLF, a secondary fermentation in wines by lactic acid bacteria during which tart tasting malic acid is converted to softer tasting lactic acid, during which carbon dioxide is generated.

Mannoprotein

A nitrogen rich protein secreted by dead yeast cells during the autolysis process that occur while the wine ages on its lees.

Marc

French for "fruit skins". See "pomace".

Mead

A wine-like alcoholic beverage made of fermented honey and water rather than grape juice.

Membrane filtration

A process of filtration that uses a thin screen of biologically inert material, perforated with microsize pores that capture matter larger than the size of the holes.

Mercaptans

Chemical compounds formed by the reaction of ethyl and methyl alcohol with hydrogen sulfide to produce a wine fault that creates odors in the wine reminiscent of burnt rubber, garlic, onions or stale cabbage.

Méthode Champenoise

(aka Methode Traditionelle, Traditional Method) Process whereby sparkling wines receive a second fermentation in the same bottle that will be sold to a retail buyer. Compare with Charmat, transfer or bulk fermented methods.

Méthode Rurale

A method of sparkling wine production similar to the Champagne method except there is no secondary fermentation. Rather the wine bottled before the primary fermentation has completed, trapping the resulting carbon dioxide gas, and leaving the residual sediment in the wine.

Microoxygenation

The controlled exposure of wine to small amounts of oxygen in the attempt to reduce the length of time required for maturation.

Microvinification

A winemaking technique often used for experimental batches of wine where the wine is fermented in small, specialized vats.

Mistelle

French term for fresh grape juice that has had alcohol added to it (Fortification) before fermentation has started. This results in a generally sweet wine.

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.

Mud

See "Lees".

Muid

French term for a large oval barrel with a capacity of 159 gallons (600 liters)

Must

Unfermented grape juice, including pips (seeds), skins and stalks.

Must weight

The level of fermentable sugars in the must and the resultant alcohol content if all the sugar was converted to ethanol.

Mutage

French term for fortifying a wine by adding alcohol to the must either before fermentation (i.e. vin de liqueur) or during (i.e. vin doux naturel)