''Brettanomyces'' is a
non-spore forming genus of
yeast
Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to consti ...
in the family
Saccharomycetaceae, and is often colloquially referred to as "Brett". The genus name ''Dekkera'' is used interchangeably with ''Brettanomyces'', as it describes the
teleomorph or
spore forming form of the yeast, but is considered deprecated under the
one fungus, one name
In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the Biological life cycle, life cycles of fungi in the Phylum, phyla Ascomycota and Basidiomycota:
*Teleomorph: the sexual reproductive stage (morph), typically a Asc ...
change. The cellular
morphology of the yeast can vary from ovoid to long "sausage" shaped cells. The yeast is
acidogenic, and when grown on
glucose
Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, usi ...
rich media under aerobic conditions, produces large amounts of
acetic acid
Acetic acid , systematically named ethanoic acid , is an acidic, colourless liquid and organic compound with the chemical formula (also written as , , or ). Vinegar is at least 4% acetic acid by volume, making acetic acid the main componen ...
. ''Brettanomyces'' is important to both the
brewing
Brewing is the production of beer by steeping a starch source (commonly cereal grains, the most popular of which is barley) in water and fermenting the resulting sweet liquid with yeast. It may be done in a brewery by a commercial brewer, ...
and
wine
Wine is an alcoholic drink typically made from fermented grapes. Yeast consumes the sugar in the grapes and converts it to ethanol and carbon dioxide, releasing heat in the process. Different varieties of grapes and strains of yeasts are ...
industries due to the sensory compounds it produces.
In the wild, ''Brettanomyces'' lives on the skins of fruit.
History
In 1889, Seyffert of the Kalinkin Brewery in St. Petersburg was the first to isolate a "''
Torula''" from English beer which produced the typical "English" taste in lager beer, and in 1899 JW Tullo at Guinness described two types of "secondary yeast" in Irish stout. However N. Hjelte Claussen at the
Carlsberg brewery was the first to publish a description in 1904, following a 1903 patent (UK patent GB190328184) that was the first patented microorganism in history. The term ''Brettanomyces'' comes from the
Greek
Greek may refer to:
Greece
Anything of, from, or related to Greece, a country in Southern Europe:
*Greeks, an ethnic group.
*Greek language, a branch of the Indo-European language family.
**Proto-Greek language, the assumed last common ancestor ...
for "British fungus".
Wine
When ''Brettanomyces'' grows in wine it produces several compounds that can alter the palate and
bouquet. At low levels some
winemakers agree that the presence of these compounds has a positive effect on wine, contributing to complexity, and giving an aged character to some young red wines. Many wines even rely on ''Brettanomyces'' to give their distinctive character, such as
Château Musar. However, when the levels of the sensory compounds greatly exceed the
sensory threshold, their perception is almost always negative. The sensory threshold can differ between individuals, and some find the compounds more unattractive than others. While it can be desirable at lower levels, there is no guarantee that high levels will not be produced. As ''Brettanomyces'' can potentially spoil a wine it is generally seen as a
wine spoilage yeast, and its presence in wine as a
wine fault.
Wines that have been contaminated with ''Brettanomyces'' taints are often referred to as "''Bretty''", "''metallic''", or as having "''Brett character''".
Also ''Brettanomyces'' taint in wine is also sometimes incorrectly identified as
cork taint
Cork taint is a broad term referring to a wine fault characterized by a set of undesirable smells or tastes found in a bottle of wine, especially spoilage that can only be detected after bottling, aging and opening. Though modern studies have s ...
.
Sensory compounds
The compounds responsible contributing certain sensory characters to wine are;
*
4-ethylphenol: Band-aids, barnyard, horse stable, antiseptic
*
4-ethylguaiacol: Bacon, spice, cloves, smoky
*
isovaleric acid: Sweaty saddle, cheese, rancidity
These compounds can impart completely different sensory properties to a wine when they are present in different ratios.
Origins in the winery
''Brettanomyces'' is most associated with barrel aged red wines, but has also been found in
Chardonnay
Chardonnay (, , ) is a green-skinned grape variety used in the production of white wine. The variety originated in the Burgundy wine region of eastern France, but is now grown wherever wine is produced, from England to New Zealand. For new ...
and
Sauvignon blanc
is a green-skinned grape variety that originates from the Bordeaux region of France. The grape most likely gets its name from the French words ''sauvage'' ("wild") and ''blanc'' ("white") due to its early origins as an indigenous grape in ...
. In some cases the yeast has caused contamination in
sparkling wines produced by the
méthode champenoise
Sparkling wine production is the method of winemaking used to produce sparkling wine. The oldest known production of sparkling wine took place in 1531 with the ''ancestral method''.
Pressure and terminology
In popular parlance and also in t ...
when ''en tirage''. It is thought ''Brettanomyces'' can be introduced to a winery by insect vectors such as
fruit flies, or by purchasing ''Brett''-contaminated wine barrels. The ability to
metabolise the
disaccharide
A disaccharide (also called a double sugar or ''biose'') is the sugar formed when two monosaccharides are joined by glycosidic linkage. Like monosaccharides, disaccharides are simple sugars soluble in water. Three common examples are sucrose, ...
cellobiose, along with the irregular surface of a barrel interior, provide ideal conditions for ''Brettanomyces'' growth. Once the yeast is in a winery it is hard to eradicate and is spread readily by unsanitised equipment.
Control measures
The growth of ''Brettanomyces'' is best controlled by the addition of
sulfur dioxide
Sulfur dioxide ( IUPAC-recommended spelling) or sulphur dioxide (traditional Commonwealth English) is the chemical compound with the formula . It is a toxic gas responsible for the odor of burnt matches. It is released naturally by volcanic ...
, to which the yeast is particularly sensitive. The addition of other sterilising compounds such as
dimethyl dicarbonate often has a similar effect. Alternatively the wine can be bottled after sterile filtration, which physically removes the yeast. Wines that are vinified to low
residual sugar levels, such as <1.0g/L, are also less likely to be spoiled as the main growth
substrate
Substrate may refer to:
Physical layers
*Substrate (biology), the natural environment in which an organism lives, or the surface or medium on which an organism grows or is attached
** Substrate (locomotion), the surface over which an organism lo ...
has been limited. However growth has been reported at levels below this and it is assumed that the yeast can use other substrates.
Beer
In most
beer
Beer is one of the oldest and the most widely consumed type of alcoholic drink in the world, and the third most popular drink overall after water and tea. It is produced by the brewing and fermentation of starches, mainly derived from cer ...
styles ''Brettanomyces'' is typically viewed as a contaminant and the characteristics it imparts are considered unwelcome "off-flavours". However, in certain styles, particularly certain traditional
Belgian ale
Beer in Belgium includes pale ales, lambics, Flemish red ales, sour brown ales, strong ales and stouts. In 2018, there were 304 active breweries in Belgium, including international companies, such as AB InBev, and traditional breweries inclu ...
s, it is appreciated and encouraged.
Gueuze and other
lambic beers owe their unique flavour profiles to ''Brettanomyces'', as do wild yeast ''
saison
Saison (French, "season," ) is a pale ale that is highly carbonated, fruity, spicy, and often bottle conditioned. It was historically brewed with low alcohol levels, but modern productions of the style have moderate to high levels of alcohol. ...
'' or farmhouse styles; and it is also found in
Oud Bruin and
Flanders red ale.
In
Orval ''Brettanomyces'' is added before the final bottle fermentation.
Several American craft breweries intentionally use ''Brettanomyces'' in their beers. This use began with a renewed interest in Belgian style ales and later formed new styles altogether (Brewers Association, 2007 Great American Beer Festival Style Guidelines, section 13a, 16). Some breweries use 100% ''Brettanomyces'' for the fermentation of some of their beers, and omit ''
Saccharomyces'' from the recipe. Some American brewers that use ''Brettanomyces'' may also include lactic acid producing bacteria such as ''
Lactobacillus'' and ''
Pediococcus'' in order to provide sourness to the beer.
While ''Brett'' is sometimes pitched into the fermenter, aging in wood barrels previously inoculated with ''Brettanomyces'' is another method used to impart the complexity contributed by these strains of yeast.
See also
*
4-ethylguaiacol
*
4-ethylphenol
* ''
Brettanomyces bruxellensis''
*
Lambic
*
Wine fault
References
*
;Footnotes
External links
Brettanomyces at Milk the Funk Wiki
{{Taxonbar, from=Q2411973
Oenology
Yeasts used in brewing
Saccharomycetes
Yeasts
de:Weinfehler#Brettanomyces