Maceration is the oenological term used to describe the process of extraction from grapes. When winemakers choose to leave skins, seeds and stems in contact with grape must, it promotes the extraction of color, aroma compounds and tannins from the crushed grape matter and subsequently increases their presence within wine.
Maceration can take place before, during or after fermentation, and there are a number of factors that determine how much influence the process has on the style of the wine being made.
The Process of Maceration
There are many different types of maceration, though the three most commonly used are: extended maceration, cold maceration and carbonic maceration. Each process utilizes extraction in a different way, or at a different time to create a distinguishably different style of wine.
Extended maceration is commonly used in the production of red wine. The process is as simple as the name suggests - increased extraction through an extended period of contact between must and skins, seeds and stems.
Vital to the success of extended maceration is a classical french technique named pigeage, which means "punching down."
During red winemaking, grapes and stems are crushed, pressed and left in contact with must. When fermentation begins, solid matter rises to the top of the fermentation vessel (propelled by carbon dioxide gas), creating what is known as a cap.
Floating on top of the fermenting grape juice, extraction from the cap is very limited. To increase maceration at this point, winemakers begin the pigeage process. By routinely punching down the cap into fermenting wine, contact between crushed grape matter and fermenting must is greatly increased.
Pigeage is essential during the production of red wine, as it enables the sufficient extraction of color and tannins, as well as importing vital aromatic and flavor compounds.
Punching down also helps to control the temperature of fermentation and decreases the amount of time required for maceration to take place. As fermentation is an exothermic reaction, pigeage ensures that heat generated can escape the insulating cap, thus inhibiting the development of "cooked" flavors in the fermenting wine. These flavors can easily build up if fermentation takes place over a long period of time.
Owing to the fact that maceration promotes the extraction of color and tannins, it stands to reason that this technique is much more useful in the production of red wine. However, maceration can also be used to capture aromatic compounds present in grapes.
Certain white grape varieties are prized for their perfumed qualities (Riesling, Muscat Blanc, Gewürztraminer etc), therefore, to increase the intensity of aromatic compounds present in these wines, winemakers turn to the cold-soak process, also known as cold maceration.
During cold maceration, must is chilled to 55° F before extraction begins. At this low temperature, fermentation can not take place and extraction is much slower. This affords the winemaker more control over extraction, allowing them to stop the process before white wines take on too much color or tannins.
When the winemaker is happy that sufficient aromatic extraction has occurred, they can easily remove grape solids and begin white wine fermentation as normal.
Carbonic Maceration is not only a different style of maceration, it is also a completely unique way of fermenting grapes into wine.
Key to this process is the introduction of whole, uncrushed, clusters into a sealed fermentation vessel filled with carbon dioxide. The presence of carbon dioxide gas inhibits natural yeast fermentation, instead encouraging naturally occurring enzymes to be released from the whole grapes. Once released, enzymes initiate fermentation, converting sugars into alcohol.
The process is unique in that while it is able to initiate fermentation, the environment is not suitable to fully ferment all sugar into alcohol. During the course of the maceration process, however, the desired amount of color can be extracted from grapes, while unique flavor and aromatic compounds simultaneously develop in the wine.
Resulting wines are notably low in tannins, another quirk of this unique process.
After carbonic maceration is complete, solids are removed before a standard form of fermentation converts remaining sugar into alcohol.
Wines that typically undergo carbonic maceration include Beaujolais Nouveau, made from Gamay grapes. This fresh, fruity red wine is notable for its lack of tannins and unique carbonic flavor compounds. Beaujolais Nouveau is also distinctive in that it is produced to be consumed during the same year that the grapes are harvested.
Maceration is one of many tools that can be used to influence the style of wine during winemaking. Carbonic Maceration in particular creates wines of a unique flavor and style that have to be tried to fully appreciate the wonders of the process.