Autolysis (wine)
Encyclopedia
Autolysis in winemaking
relates to the complex chemical reactions that take place when a wine spends time in contact with the lees, or dead yeast
cells, after fermentation
. While for some wine
s autolysis is undesirable, it is a vital component in shaping the flavors and mouth feel associated with premium Champagne production. The practice of leaving a wine to age on its lees (or sur lie aging) has a long history in winemaking dating back to Roman winemaking. The chemical process and details of autolysis were not originally understood but the positive effects of a creamy mouthfeel, breadlike and floral aroma, as well as reduced astringency were noticed early on.
, observed that wine that was left on its lees (or sediment as they knew it) exhibited different characteristics than wine that was quickly separated from its sediment. While the Romans did not understand the full chemical process or details behind the autolysis that took place, they were able to perceive the results of this autolysis in the creamy mouthfeel, reduced astringency and unique flavors and aromas that developed. With modern day understanding of autolysis, winemaking in the Champagne have strict regulation regarding the time Champagne must spend in contact with its lees in order to receive some benefit from autolysis. Under Appellation d'origine contrôlée
(AOC) regulations, wines from Champagne cannot legally be sold until it has gone through autolysis in the bottle for at least 15 months with non-vintage
Champagne. Vintage Champagne must have a minimum of 3 years aging with some Champagne houses extending the time for autolysis to nearly 7 years.
During fermentation, yeast cells convert the sugar in the grape must into ethanol
. When the sugar food source for the yeast and necessary nutrients such as nitrogen
run out, or the alcohol level of the wine reaches such as point to where it is toxic for the yeast, the cells die and sink to the bottom of the fermentation vessel. These dead cells, or "lees", are normally removed by racking
the wine into a clean vessel. If the wine is left in contact with the lees, enzymes start to break the cells down producing mannoproteins (mannose
-containing glycoproteins) and polysaccharides that are released into the wine. In sparkling wine production
, a wine is made "sparkling" or "bubbly" because a secondary fermentation
is introduced when the wine is contained within a sealed wine bottle
. During this time the wine is deliberately kept in contact with its lees inside the bottle for a period ranging from a couple months to several years. Studies have shown that the chemical reaction of autolysis, and its impact on the wine, starts to become noticeable after 18 months and will continue to impart traits for at least 5 years. The sparkling wine is eventually separated from its lees through a technique known as riddling and disgorgement.
s that are precipitated out. They may also bind with the tannins in the wine to reduce the perception of bitterness or astringency in the wine. The increased production of amino acid
s leads to the develop of several flavors associated with premium Champagne including aromas of biscuit
s or bread
dough
, nut
tiness and acacia
. As the wine ages further, more complex notes may develop from the effects of autolysis.
s can potentially develop from autolysis. If the layer of lees begins to exceed 4 inches (10 centimeters), the enzymes released from the process of the yeast digesting themselves creates reducing
conditions and promotes the development of hydrogen sulfide
and mercaptan odors. The process of stirring the lees or bâttonage can help prevent a thick layer of lees forming and promote a smoother autolysis. Poor hygiene of the winemaking equipment or wine made from grapes that had residue from fungicide
can create off odors smelling of sulfide
.
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...
relates to the complex chemical reactions that take place when a wine spends time in contact with the lees, or dead yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
cells, after fermentation
Fermentation (wine)
The process of fermentation in wine turns grape juice into an alcoholic beverage. During fermentation, yeast interact with sugars in the juice to create ethanol, commonly known as ethyl alcohol, and carbon dioxide...
. While for some wine
Wine
Wine is an alcoholic beverage, made of fermented fruit juice, usually from grapes. The natural chemical balance of grapes lets them ferment without the addition of sugars, acids, enzymes, or other nutrients. Grape wine is produced by fermenting crushed grapes using various types of yeast. Yeast...
s autolysis is undesirable, it is a vital component in shaping the flavors and mouth feel associated with premium Champagne production. The practice of leaving a wine to age on its lees (or sur lie aging) has a long history in winemaking dating back to Roman winemaking. The chemical process and details of autolysis were not originally understood but the positive effects of a creamy mouthfeel, breadlike and floral aroma, as well as reduced astringency were noticed early on.
History
Ancient Roman writers, like Marcus Porcius CatoMarcus Porcius Cato
Marcus Porcius Cato may refer to:*Cato the Elder , born Marcus Porcius Priscus and then nicknamed Cato*Marcus Porcius Cato Licinianus , son of Cato the elder by his first wife...
, observed that wine that was left on its lees (or sediment as they knew it) exhibited different characteristics than wine that was quickly separated from its sediment. While the Romans did not understand the full chemical process or details behind the autolysis that took place, they were able to perceive the results of this autolysis in the creamy mouthfeel, reduced astringency and unique flavors and aromas that developed. With modern day understanding of autolysis, winemaking in the Champagne have strict regulation regarding the time Champagne must spend in contact with its lees in order to receive some benefit from autolysis. Under Appellation d'origine contrôlée
Appellation d'Origine Contrôlée
Appellation d’origine contrôlée , which translates as "controlled designation of origin", is the French certification granted to certain French geographical indications for wines, cheeses, butters, and other agricultural products, all under the auspices of the government bureau Institut National...
(AOC) regulations, wines from Champagne cannot legally be sold until it has gone through autolysis in the bottle for at least 15 months with non-vintage
Vintage
Vintage, in wine-making, is the process of picking grapes and creating the finished product . A vintage wine is one made from grapes that were all, or primarily, grown and harvested in a single specified year. In certain wines, it can denote quality, as in Port wine, where Port houses make and...
Champagne. Vintage Champagne must have a minimum of 3 years aging with some Champagne houses extending the time for autolysis to nearly 7 years.
Process
Ethanol
Ethanol, also called ethyl alcohol, pure alcohol, grain alcohol, or drinking alcohol, is a volatile, flammable, colorless liquid. It is a psychoactive drug and one of the oldest recreational drugs. Best known as the type of alcohol found in alcoholic beverages, it is also used in thermometers, as a...
. When the sugar food source for the yeast and necessary nutrients such as nitrogen
Nitrogen
Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless, and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere...
run out, or the alcohol level of the wine reaches such as point to where it is toxic for the yeast, the cells die and sink to the bottom of the fermentation vessel. These dead cells, or "lees", are normally removed by racking
Racking
Racking is the process of siphoning the wine or beer off the lees into a new, clean barrel or in the case of beer off the trub. Racking allows clarification and aids in stabilization. Wine that is allowed to age on the lees often develops "off-tastes". A racking hose or tubing is used and can be...
the wine into a clean vessel. If the wine is left in contact with the lees, enzymes start to break the cells down producing mannoproteins (mannose
Mannose
Mannose is a sugar monomer of the aldohexose series of carbohydrates. Mannose is a C-2 epimer of glucose. It is not part of human metabolism, but is a component of microbial cell walls, and is therefore a target of the immune system and also of antibiotics....
-containing glycoproteins) and polysaccharides that are released into the wine. 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...
, a wine is made "sparkling" or "bubbly" because a secondary fermentation
Secondary fermentation
Secondary fermentation is a process commonly associated with winemaking, which entails a second period of fermentation 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 or stainless steel tank and then...
is introduced when the wine is contained within a sealed wine bottle
Wine bottle
A wine bottle is a bottle used for holding wine, generally made of glass. Some wines are fermented in the bottle, others are bottled only after fermentation. They come in a large variety of sizes, several named for Biblical kings and other figures. The standard bottle contains 750 ml,...
. During this time the wine is deliberately kept in contact with its lees inside the bottle for a period ranging from a couple months to several years. Studies have shown that the chemical reaction of autolysis, and its impact on the wine, starts to become noticeable after 18 months and will continue to impart traits for at least 5 years. The sparkling wine is eventually separated from its lees through a technique known as riddling and disgorgement.
Influences on the wine
The effects of autolysis on wine contributes to a creamy mouthfeel that may make a wine seem to have a fuller body. The release of enzymes inhibits oxidation which improves some of the aging potential of the wine. The mannoproteins improve the overall stability of the proteins in the wine by reducing the amount of tartrateTartrate
A tartrate is a salt or ester of the organic compound tartaric acid, a dicarboxylic acid. Its formula is O−OC-CH-CH-COO− or C4H4O62−.As food additives, tartrates are used as antioxidants, acidity regulators, and emulsifiers...
s that are precipitated out. They may also bind with the tannins in the wine to reduce the perception of bitterness or astringency in the wine. The increased production of amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
s leads to the develop of several flavors associated with premium Champagne including aromas of biscuit
Biscuit
A biscuit is a baked, edible, and commonly flour-based product. The term is used to apply to two distinctly different products in North America and the Commonwealth Nations....
s or bread
Bread
Bread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...
dough
Dough
Dough is a paste made out of any cereals or leguminous crops by mixing flour with a small amount of water and/or other liquid. This process is a precursor to making a wide variety of foodstuffs, particularly breads and bread-based items , flatbreads, noodles, pastry, and similar items)...
, nut
Nut (fruit)
A nut is a hard-shelled fruit of some plants having an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts...
tiness and acacia
Acacia
Acacia is a genus of shrubs and trees belonging to the subfamily Mimosoideae of the family Fabaceae, first described in Africa by the Swedish botanist Carl Linnaeus in 1773. Many non-Australian species tend to be thorny, whereas the majority of Australian acacias are not...
. As the wine ages further, more complex notes may develop from the effects of autolysis.
Potential faults
If not properly managed, wine faultWine fault
A wine fault or defect is an unpleasant characteristic of a wine often resulting from poor winemaking practices or storage conditions, and leading to wine spoilage. Many of the compounds that cause wine faults are already naturally present in wine but at insufficient concentrations to adversely...
s can potentially develop from autolysis. If the layer of lees begins to exceed 4 inches (10 centimeters), the enzymes released from the process of the yeast digesting themselves creates reducing
Redox
Redox reactions describe all chemical reactions in which atoms have their oxidation state changed....
conditions and promotes the development of hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
and mercaptan odors. The process of stirring the lees or bâttonage can help prevent a thick layer of lees forming and promote a smoother autolysis. Poor hygiene of the winemaking equipment or wine made from grapes that had residue from fungicide
Fungicide
Fungicides are chemical compounds or biological organisms used to kill or inhibit fungi or fungal spores. Fungi can cause serious damage in agriculture, resulting in critical losses of yield, quality and profit. Fungicides are used both in agriculture and to fight fungal infections in animals...
can create off odors smelling of sulfide
Sulfide
A sulfide is an anion of sulfur in its lowest oxidation state of 2-. Sulfide is also a slightly archaic term for thioethers, a common type of organosulfur compound that are well known for their bad odors.- Properties :...
.
External links
- M. J. Leroy et al. "Yeast Autolysis During Champagne Aging" American Society for Enology and Viticulture. 41:1:21-28 (1990)
- M. Feuillat & C. Charpentier "Autolysis of Yeasts in Champagne" American Society for Enology and Viticulture Am. J. Enol. Vitic. 33:1:6-13 (1982)