Secondary fermentation is a process commonly associated with winemaking

Winemaking

Winemaking, or vinification, is the production of wine, starting with selection of the grapes or other produce and ending with bottling the finished wine. Although most wine is made from grapes, it may also be made from other fruit or non-toxic plant material...

, which entails a second period of fermentation

Ethanol fermentation

Ethanol fermentation, also referred to as alcoholic fermentation, is a biological process in which sugars such as glucose, fructose, and sucrose are converted into cellular energy and thereby produce ethanol and carbon dioxide as metabolic waste products...

 in a different vessel than what was used when the fermentation process first started. An example of this would be starting fermentation in a carboy

Carboy

A carboy is a rigid container with a typical capacity of 5 to 15 gallons . Carboys are primarily used for transporting fluids, often water or chemicals.They are also used for in-home fermentation of beverages, often wine.-Brewing:...

 or stainless steel tank and then moving it over to oak barrels. Rather than being a separate, second fermentation, this is most often one single fermentation period that is conducted in multiple vessels. However, the term does also apply to procedures that could be described as a second and distinct fermentation period.

In wine production

In sparkling wine production

Sparkling wine production

There are four main methods of sparkling wine production. The first is simple injection of carbon dioxide , the process used in soft drinks, but this produces big bubbles that dissipate quickly in the glass. The second is the Metodo Italiano – Charmat process, in which the wine undergoes a...

, the secondary fermentation often takes places in the wine bottle that the wine will be sold in. This is most commonly known as the méthode champenoise or "Champagne method" after the region most noted for sparkling wine production. When the base wine (or cuvee

Cuvee

Cuvée is a French wine term derived from cuve, meaning vat or tank. The term cuvée is used with several different meanings, more or less based on the concept of a tank of wine put to some purpose:...

) has been produced from single grape varietal

Varietal

"Varietal" describes wines made primarily from a single named grape variety, and which typically displays the name of that variety on the wine label. Examples of grape varieties commonly used in varietal wines are Cabernet Sauvignon, Chardonnay and Merlot...

s or a blend, the wine is bottled with a mixture of yeast and fresh sugar known as the "liqueur de tirage". This secondary fermentation, also known as bottle fermentation, is the process that makes the wine "bubbly" due to the containment of carbon dioxide

Carbon dioxide

Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 which is normally released as a by product in regular fermentation.

In still wine production, particularly of red wines and some white wines like Chardonnay

Chardonnay

Chardonnay is a green-skinned grape variety used to make white wine. It is originated from the Burgundy wine region of eastern France but is now grown wherever wine is produced, from England to New Zealand...

, the secondary fermentation process can also usher in the use of malolactic fermentation

Malolactic fermentation

Malolactic fermentation is a process in winemaking where tart-tasting malic acid, naturally present in grape must, is converted to softer-tasting lactic acid. Malolactic fermentation tends to create a rounder, fuller mouthfeel. It has been said that malic acid tastes of green apples...

 (or MLF) where the hard, green apple-like malic acid

Malic acid

Malic acid is an organic compound with the formula HO2CCH2CHOHCO2H. It is a dicarboxylic acid which is made by all living organisms, contributes to the pleasantly sour taste of fruits, and is used as a food additive. Malic acid has two stereoisomeric forms , though only the L-isomer exists...

 is converted into softer, butter-like lactic acid

Lactic acid

Lactic acid, also known as milk acid, is a chemical compound that plays a role in various biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid with the chemical formula C3H6O3...

. In the case of a stuck fermentation

Stuck fermentation

A stuck fermentation occurs in brewing beer or winemaking when the yeast become dormant before the fermentation has completed. Unlike an "arrested fermentation" where the winemaker intentionally stops fermentation , a stuck fermentation is an unintentional and unwanted occurrence that can lead to...

, a winemaker may wish to transfer the must

Must

Must is freshly pressed fruit juice that contains the skins, seeds, and stems of the fruit. The solid portion of the must is called pomace; it typically makes up 7%–23% of the total weight of the must. Making must is the first step in winemaking...

 to a second vessel and use stronger, more aggressive yeasts with high fermentation temperatures to re-initiate the fermentation process. A similar process known as governo

Governo

Governo is a winemaking technique reportedly invented in Tuscany in 14th century to help complete fermentation and stabilize the wine. The technique involves saving a batch of harvested grape and allowing them to partially dry...

has been used by Tuscan winemakers since the 14th century with the isolation after harvest

Harvest (wine)

The harvesting of wine grapes is one of the most crucial steps in the process of winemaking. The time of harvest is determined primarily by the ripeness of the grape as measured by sugar, acid and tannin levels with winemakers basing their decision to pick based on the style of wine they wish to...

of a batch of grapes that can be added later to the wine to help prevent or recovery from a stuck fermentation.

Further reading

• Jeff Cox "From Vines to Wines: The Complete Guide to Growing Grapes and Making Your Own Wine" Storey Publishing 1999 ISBN 1580171052
• William Patton "The laws of fermentation and the wines of the ancients" University of Michigan Publishing 2005 ISBN 1425509282

External links

• SQ Liu "Malolactic fermentation in wine - beyond deacidification" - Journal of Applied Microbiology, 2002 Volume 92 Issue 4 Page 589-601
• American Journal of Enology and Viticulture "Studies on the Secondary Fermentation of Low-Alcohol Sparkling Apple Wine" 44:1:93-98 (1993)
• Winemaking basics "Transfer to secondary"