Brettanomyces
Brettanomyces, also known as brett or bretta, is a yeast that was originally thought of as a spoilage yeast. Known for it's barnyard, fecal, horsey, metallic or Band-Aid flavors, brett was unwelcome in most breweries. However, in some styles like Saison and Lambic these flavors add a layer of complexity to the beer. See Lactobacillus, Pediococcus, Saccharomyces, and Mixed Cultures charts for other commercially available cultures.
Contents
Brettanomyces Metabolism
Carbohydrate Metabolism
Brettanomyces strains may possess both alpha and beta glucosidases. These enzymes allow Brettanomyces strains to break down longer chain carbohydrate molecules and to liberate glycosidically bound sugars which are unfermentable to Saccharomyces yeasts.
Glycosides are sugar molecules connected to other organic compounds such as acids, alcohols, and aldehydes which are flavor and aroma inactive due to the sugar molecule attached. By cleaving off the sugar molecule through glucosidase activity, Brettanomyces species can liberate these compounds (called aglycones) into their aroma-active and flavor-active states, or states that may become flavor and aroma active through further modification[1]. Therefore Brettanomyces strains are able to produce novel flavors and aromas from hops, fruits, and fruit pits that Saccharomyces yeasts cannot produce. In addition, the liberated aroma and flavor active compounds may be further processed by Brettanomyces through ester production or destruction pathways.
Ester Production and Destruction
Brettanomyces is capable of forming several ethyl esters (derived from ethanol and fatty acids). Among these are ethyl acetate, ethyl lactate and phenethyl acetate, along with the hydrolysis of isoamyl acetate. During non-mixed fermentations where lactic acid and acetic acid are minimal to none, these esters are produced in smaller quantities [2].
| Ester | Precursors | Flavor/Odor Threshold | Notes |
|---|---|---|---|
| Ethyl acetate (Fruity, Solventy) | Acetic Acid | 33ppm (odor), 100ppm (flavor) | High flavor threshold; pear-like in low amounts and nail polish in high amounts. Increases production with higher temperatures and oxygen |
| Ethyl lactate (Fruity, buttery) | Lactic Acid | 0.2 ppm-1.66 ppm (odor) [3] | Increases production with higher amounts of Lactic Acid |
| Phenethyl acetate (Sweet, Honey, Rose flower like) | Acetyl-CoA, 2-phenylethanol | 3-5ppm (odor), 5-10ppm (flavor) [4] | [5] |
| Ethyl butyrate (Pineapple) | Butyric Acid | Low levels of production by some species of Brettanomyces; production decreases with higher acidity [6] | |
| Ethyl Decanoate (Brandy, Fruity, oily, Grape) | Capric Acid (Decanoic acid) | Also known as Ethyl Caprate [7] | |
| Isoamyl Acetate (Banana) | Acetic acid, Isoamyl alcogol | Produced by certain Saccharomyces strains but concentrations are generally reduced by Brettanomyces. [8] |
Phenol Production
Phenols such as 4-vinylphenol (4VP, barnyard, medicinal) and 4-vinylguaiacol (4-VG, clove) can be produced in beer by the decarboxylation of hydoxycinnamic acids, which are found in malt. While both Saccharomyces and Brettanomyces strains are capable of converting hydroxycinnamic acids to their vinyl derivatives, Brettanomyces is also able to reduce these vinyl derivatives to ethyl derivatives. These vinyl derivatives have similar tastes to the ethyl derivatives but have lower flavor thresholds.
| Phenol | Phenol Type | Precursors |
|---|---|---|
| 4-vinylphenol (Barnyard, Medicinal, Band-aid, Plastic) | Vinyl phenol | P-Courmaric Acid |
| 4-vinylguiacol (Clove) | Vinyl phenol | Ferulic Acid |
| Vinyl catechol (Plastic, Bitter, Smokey) | Vinyl phenol | Caffeic Acid |
| 4-ethylphenol (Barnyard, Spicy, Smoky) | Ethyl phenol | 4-vinylphenol |
| 4-ethylguiacol (Smokey, Spicy, Clove) | Ethyl phenol | 4-vinylguiacol |
| Ethyl catechol (Band‐aide, Medicinal, Barnyard) | Ethyl phenol | Vinyl catechol |
Acid Production
In the presence of oxygen, Brettanomyces strains are capable of producing acetic acid. Depending on the brewer's palate and the degree of acetic production, this can be a desirable or undesirable trait. The degree of acetic acid production varies among different brett strains. Acetic acid produced by Brettanomyces may also be used in the synthesis of acetate esters such as ethyl acetate. Brett has been shown to produce enough fatty acids in anaerobic fermentation to drop the pH to 4.0, which can also be esterified (see the ester table above) [6]. Many of these acids can have an unpleasant rancid odor and/or taste, which may be noticeable in young Brettanomyces beers before these acids are esterified.
| Acids Produced | Precursors | Notes |
|---|---|---|
| Acetic Acid (Vinegar, harsh acidity) | Oxygen | Increased production with higher levels of oxygen exposure. |
| Isovaleric Acid (Feety, Rancid parmesian) [11][12] | Leucine | Commonly described as a "spoilage" acid produced by Brettanomyces in wine, but also appears in beer. |
| Caproic acid (Fatty, cheesy, waxy, barnyardy) [6] | Fatty acid. | |
| Enanthic acid (Rancid odor) [6] | Fatty acid. | |
| Caprylic acid (Rancid-like smell and taste [6] | Fatty acid. Also found in milk. | |
| Pelargonic acid (Rancid odor) [6] | Fatty acid. | |
| Capric acid (Barnyard animal odor/taste) [6] | Fatty acid. Also found in milk, coconut oil, and seed oils [13]. | |
| Undecylic acid [6] | Fatty acid. | |
| Lauric acid (faint odor of bay oil or soap) [6] | Fatty acid. |
Brett Strains
Isolates
In cooperation with Funk Factory
| Common Name | Species Name | Synonym (Strain) Name | Lab/Package | Flavor/Aroma | Source Note | |
|---|---|---|---|---|---|---|
| Anomala | Dekkera anomala | B. intermedius | ECY-04 | strong ester profile with some light funk and acidity | beer - Adelaide, Australia | |
| Anomalus | Dekkera anomala | B. anomalus | Wyeast | bottled stout - Burton on Trent, England | ||
| Bruxellensis | Dekkera bruxellensis | B. bruxellensis | BSI | Same as White Labs | Pro-Brewers only. | |
| Bruxellensis | Dekkera bruxellensis | B. bruxellensis | WLP650 | Barnyard | Not the same as WY's Brux | |
| Bruxellensis | Dekkera bruxellensis | B. bruxellensis | Wyeast 5112 | "sweaty horse blanket" | Not the same as WL's Brux | |
| Bruxellensis | Dekkera bruxellensis | B. bruxellensis | ECY-05 | funky with barnyard notes accompanied by some fruit | isolated from Belgian stout | |
| Bruxellensis | Dekkera bruxellensis | B. bruxellensis | RVA 502 | A medium-intensity Brettanomyces yeast strain. Will add a bit of funk when added during the secondary. Typically used in Belgian-style beers, especially lambic. A famous Trappist brewery produces its unique beer with this yeast during secondary fermentation. | RVA Yeast Labs | |
| Bruxellensis | Dekkera bruxellensis | B. bruxellensis | GB144 | Produces a sweet, slightly fruity profile with just a hint of barnyard and spicy phenolics | GigaYeast | |
| Claussenii | Dekkera anomala | B. claussenii | BSI | Same as White Labs | Pro-Brewers only. | |
| Claussenii | Dekkera anomala | B. claussenii | WLP645 | Fruity, pineapple | ||
| Claussenii | Dekkera anomala | B. claussenii | RVA 501 | A low-intensity strain. Contributions from this strain are mostly aromas of pineapple and fruit. This strain prefers higher temperatures (85º F), but will produce nice aroma and subtle flavor at normal ale fermentation termperatures (68-72º F). | RVA Yeast Labs | |
| CMY1 | Dekkera bruxellensis | B. bruxellensis CMY1 | BSI | Chad Yakobson's mutation of BSI Drie | ||
| Custersianus | Dekkera custersiana | B. custersianus | ECY-19 | light fruit and hay | Bantu beer brewery, South Africa | |
| Drie | Dekkera bruxellensis | B. drei | BSI | "highly aromatic" | Isolate from Drie Fonteinen; Pro-Brewers only. | |
| Farmhouse | ? | B. fantome | ECY-03 | Fruity and funky profile with some acidity gradually increasing over time. Aeration has more of a muted effect | Isolate from Fantome | |
| Lambicus | Dekkera bruxellensis | B. lambicus | BSI | Same as White Labs | Pro-Brewers only. | |
| Lambicus | Dekkera bruxellensis | B. lambicus | WLP653 | Horsey, Smoky, Spicy | Different from WY's "lambicus" | |
| Lambicus | Dekkera bruxellensis | B. lambicus | Wyeast 5526 | Pie-cherry | Different from WL's "lambicus" | |
| Lambicus | Dekkera bruxellensis | B. lambicus | RVA 503 | High-intensity “Brett” strain. Very spicey with “smoky” and “horseblanket” flavors and aromas. This strain is used mostly in Lambics and Flanders sour beers. | RVA Yeast Labs | |
| Naardenensis | Dekkera naardenensis | B. naardenensis | ECY-30 | strawberry, honey, ripe fruit with a tart, citrusy acidity after 6mo of aging | Isolated from Dr. Pepper | |
| Nanus | Eeniella nana | B. nanus | ECY-24 | spicy, saison-like profile | bottled beer - Kalmar, Sweden | |
| Trois | WLP644 | Mango, Pineapple | Isolate from Drie Fonteinen, DISCOVERED NOT TO BE BRETT ON 12/10/2014 | |||
| Unknown | Unknown | Unknown | RVA 804 | Produces some amazing aromas of pears, and other fruit esters. We highly recommend this strain for Belgian Dubbels. This strain also makes a very nice cider. A highly flocculating, medium-high attenuating strain adds nice complexity to stouts, and Belgian Ales and Specialty Belgian Ales. Flocculation: Medium, Attenuation: 78-85%, Suggested Temp Range: 65-72°F, Alcohol Tolerance: 14%. | This strain originates from local fruit trees. |
Smaller Labs
| Mfg | Taxonomy | Notes |
|---|---|---|
| BKYeast | Brett X1 | Suspected Brettanomyces Anomalus |
| BKYeast | Brett C1 | Isolate from Cantillon Iris |
| BKYeast | Brett C2 | Isolate from Cantillon Iris |
| BKYeast | Brett C3 | Isolate from Cantillon Iris |
| DCYeast | DCY01 | |
| Saccharolicious | Brett I | |
| Saccharolicious | Brett II | originates from Brasserie à Vapeur in Pipaix, Belgium, and was isolated from a bottle of Cochonne |
Brett Blends
| Manufacturer | Common Name | Notes |
|---|---|---|
| East Coast Yeast | ECY34 | Twelve (12) different isolates of Brettanomyces exhibiting high production of barnyard "funk" and esters. Dryness, ripe fruit, and acidity will be encountered over a period of months and over time (>1 yr), may display gueuze-like qualities in complexity. Contains various isolates from lambic-producers, B. bruxellensis, B. anomala, B. lambicus, and B. naardenensis. For those who want the most from Brett yeast, whether a 100% Brett fermentation is desired or adding to secondary aging projects. Suggested fermentation temperature: 60-74 F. Attenuation high. |
| The Yeast Bay | Beersel | not overly funky but there is a sweaty note hanging behind lemon and citrus fruits, nice blend of subtle funk and citrus/fruit |
| The Yeast Bay | Brussels | similar to Beersel but with more funk in aroma and less fruit, complex barnyard character |
| The Yeast Bay | Lochristi | Smells of Iris C2, probably the same, subtle blend with some delicate fruit, strawberry |
| The Yeast Bay | Amalgamation Brett Super Blend | 6 Brett blend to create a dry beer with a bright and complex fruit-forward flavor and aroma, accompanied by some funk |
See Also
References
- ↑ Daenen et al., 2008. Evaluation of the glycoside hydrolase activity of a Brettanomyces strain on glycosides from sour cherry (Prunus cerasus L.) used in the production of special fruit beers. FEMS Yeast Res. 8, 1103-1114.
- ↑ Yakobson, Chad. Pure Culture Fermentation Characteristics of Brettanomyces Yeast Species and Their Use in the Brewing Industry. Production of Secondary Metabolites. 2011.
- ↑ Haz-Map, Ethyl Lactate odor threshold.
- ↑ Burdock, George A. Fenaroli's Handbook of Flavor Ingredients, Fifth Edition. CRC Press. 2005. pg 1521.
- ↑ YMDB. Phenethyl acetate.
- ↑ 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 Yakobson, Chad. Pure Culture Fermentation Characteristics of Brettanomyces Yeast Species and Their Use in the Brewing Industry. Pure Culture Fermentation Discussion. 2011.
- ↑ Spedding, Gary. Flavor notes for Michigan Craft Guild Conference. 2014.
- ↑ Spaepen and Verachtert, 1982. Esterase Activity in the Genus Brettanomyces
- ↑ Doss, Greg. Brettanomyces: Flavors and performance of single and multiple strain fermentations with respect to time. Presentation at 2008 NHC. pg 12.
- ↑ Yakobson, Chad. Brettanomyces in Brewing the horse the goat and the barnyard. 1/14/2011
- ↑ Botha, Janita J. Sensory, chemical and consumer analysis of Brettanomyces spoilage in South African wines. March 2010. Pg 2, 13, 17, 18
- ↑ Oelofse, Adriaan. Investigating the role of Brettanomyces and Dekkera during winemaking. December 2008.
- ↑ "Decanoic acid". Wikipedia.