Difference between revisions of "Tetrahydropyridine"
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| − | + | Forms of '''Tetrahydropyridine''' (specifically 6-Acetyl-2,3,4,5-tetrahydropyridine [<nowiki />ATHP/ACTPY] and 2-acetyl-1-pyrroline [<nowiki />ACPY] <ref name="wikipedia">[http://en.wikipedia.org/wiki/6-Acetyl-2,3,4,5-tetrahydropyridine 6-Acetyl-2,3,4,5-tetrahydropyridine. Wikipedia. Retrieved 3/210/2015.]</ref>, which are classified as ketones <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1034461653248715/?comment_id=1034611563233724&offset=0&total_comments=29 Humbard, Matt. Milk The funk Discussion. 3/10/2015.]</ref>) are commonly attributed to the ''mousy'', ''urine'' (in high amounts) ''cheerios'' (in low amounts), ''breakfast cereal'', or more generically, ''cracker biscuit'' flavor in sour beers. The flavor is detected towards the end of the swallow. The exact cause of this perceived flavor is not definitive. Diacetyl has also been indicated as a potential cause to this flavor in sour beers. However, ''Tetrahydropyridine'' seems to be the most likely cause. The flavor tends to age out of sour beers, although the exact mechanism for this is not fully understood <ref>[http://www.homebrewtalk.com/f127/cheerios-character-after-bottling-504468/#post6516169 Tonsmeire, Michael. Homebrewtalk.com post 1. 11/21/2014. Retrieved 3/10/2015.]</ref>. Michael Tonsmeire also noticed that pitching rehydrated wine yeast at bottling reduces the amount/duration of this flavor <ref>[http://www.homebrewtalk.com/f127/cheerios-character-after-bottling-504468/#post6522207 Tonsmeire, Michael. Homebrewtalk.com post 2. 11/21/2014. Retrieved 3/10/2015.]</ref>. | |
| − | Forms of ''Tetrahydropyridine'' (specifically 6-Acetyl-2,3,4,5-tetrahydropyridine [<nowiki />ATHP/ACTPY] and 2-acetyl-1-pyrroline [<nowiki />ACPY] <ref name="wikipedia">[http://en.wikipedia.org/wiki/6-Acetyl-2,3,4,5-tetrahydropyridine 6-Acetyl-2,3,4,5-tetrahydropyridine. Wikipedia. Retrieved 3/210/2015.]</ref>, which are classified as ketones <ref>[https://www.facebook.com/groups/MilkTheFunk/permalink/1034461653248715/?comment_id=1034611563233724&offset=0&total_comments=29 Humbard, Matt. Milk The funk Discussion. 3/10/2015.]</ref>) are commonly attributed to the ''mousy'', ''urine'' (in high amounts) ''cheerios'' (in low amounts), ''breakfast cereal'', or more generically, ''cracker biscuit'' flavor in sour beers. The flavor is detected towards the end of the swallow. The exact cause of this perceived flavor is not definitive. Diacetyl has also been indicated as a potential cause to this flavor in sour beers. However, ''Tetrahydropyridine'' seems to be the most likely cause. The flavor tends to age out of sour beers, although the exact mechanism for this is not fully understood <ref>[http://www.homebrewtalk.com/f127/cheerios-character-after-bottling-504468/#post6516169 Tonsmeire, Michael. Homebrewtalk.com post 1. 11/21/2014. Retrieved 3/10/2015.]</ref>. Michael Tonsmeire also noticed that pitching rehydrated wine yeast at bottling reduces the amount/duration of this flavor <ref>[http://www.homebrewtalk.com/f127/cheerios-character-after-bottling-504468/#post6522207 Tonsmeire, Michael. Homebrewtalk.com post 2. 11/21/2014. Retrieved 3/10/2015.]</ref>. | ||
In food, ''Tetrahydropyridine'' is associated with the aroma of baked goods such as white bread, popcorn, and tortillas, and is formed by Maillard reactions during heating. ATHP and ACPY have an odor threshold of 0.06ng/l <ref name="wikipedia"></ref>. | In food, ''Tetrahydropyridine'' is associated with the aroma of baked goods such as white bread, popcorn, and tortillas, and is formed by Maillard reactions during heating. ATHP and ACPY have an odor threshold of 0.06ng/l <ref name="wikipedia"></ref>. | ||
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Traditionally, the mousy/cheerios flavor from THP is considered an off flavor in both wine and sour beer. There is some debate and differing opinions as to whether or not a small amount of THP flavor is allowable (or even enjoyable) in sour beers, however most consider any level to be an off flavor. | Traditionally, the mousy/cheerios flavor from THP is considered an off flavor in both wine and sour beer. There is some debate and differing opinions as to whether or not a small amount of THP flavor is allowable (or even enjoyable) in sour beers, however most consider any level to be an off flavor. | ||
| − | =Production= | + | ==Production== |
''Editor's note: special thanks to [http://www.homebrewtalk.com/f127/brett-strain-production-athp-449852/ ne0t0ky0] on Homebrewtalk for collecting some of these resources.'' | ''Editor's note: special thanks to [http://www.homebrewtalk.com/f127/brett-strain-production-athp-449852/ ne0t0ky0] on Homebrewtalk for collecting some of these resources.'' | ||
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Some species of [[Pediococcus]] have been associated with the production of ATHP. In particular, these include ''P. pentosaceus'' <ref>[http://www.uniprot.org/uniprot/Q03HT0 UniProt article. Retrieved 3/10/2015.]</ref><ref>[http://www.uniprot.org/uniprot/U5ZF76 UniProt article. Retrieved 3/10/2015.]</ref>, and ''P. clausenii'' <ref>[http://www.uniprot.org/uniprot/G8PEU4 UniProt article. Retrieved 3/10/2015.]</ref>. | Some species of [[Pediococcus]] have been associated with the production of ATHP. In particular, these include ''P. pentosaceus'' <ref>[http://www.uniprot.org/uniprot/Q03HT0 UniProt article. Retrieved 3/10/2015.]</ref><ref>[http://www.uniprot.org/uniprot/U5ZF76 UniProt article. Retrieved 3/10/2015.]</ref>, and ''P. clausenii'' <ref>[http://www.uniprot.org/uniprot/G8PEU4 UniProt article. Retrieved 3/10/2015.]</ref>. | ||
| − | =Thresholds= | + | ==Thresholds== |
''Editor's note: the following thresholds are from a study on wine, and may not hold true for beer.'' | ''Editor's note: the following thresholds are from a study on wine, and may not hold true for beer.'' | ||
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** Concentration reported in wines exhibiting mousy off-flavour: Tr-7.8 µg/L <ref>[http://kb.osu.edu/dspace/bitstream/handle/1811/56335/OARDC_HCS_0744_ppt_18_Gerstenbriand.pdf?sequence=27 Malolactic Fermentation 2005. Geneva on the Lake. Feb 2005. Retrieved 3/10/2015.]</ref> | ** Concentration reported in wines exhibiting mousy off-flavour: Tr-7.8 µg/L <ref>[http://kb.osu.edu/dspace/bitstream/handle/1811/56335/OARDC_HCS_0744_ppt_18_Gerstenbriand.pdf?sequence=27 Malolactic Fermentation 2005. Geneva on the Lake. Feb 2005. Retrieved 3/10/2015.]</ref> | ||
| − | =Discussions= | + | ==Discussions== |
Below is a list of discussions on internet forum threads that may shed light on specific strains and individual experiences. Keep in mind that many of the opinions and experiences are anecdotal, although commonalities and shared experiences may prove to be useful and accurate. | Below is a list of discussions on internet forum threads that may shed light on specific strains and individual experiences. Keep in mind that many of the opinions and experiences are anecdotal, although commonalities and shared experiences may prove to be useful and accurate. | ||
* [https://www.facebook.com/groups/MilkTheFunk/permalink/1034461653248715/ Milk The Funk Thread] | * [https://www.facebook.com/groups/MilkTheFunk/permalink/1034461653248715/ Milk The Funk Thread] | ||
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* [http://www.babblebelt.com/newboard/thread.html?tid=1108752780&th=1277680358 Babblebelt thread with comments by Chad Yakobson] | * [http://www.babblebelt.com/newboard/thread.html?tid=1108752780&th=1277680358 Babblebelt thread with comments by Chad Yakobson] | ||
| − | =References= | + | ==References== |
<references/> | <references/> | ||
| + | |||
[[Category:Compounds]] | [[Category:Compounds]] | ||
Revision as of 09:26, 17 March 2015
Forms of Tetrahydropyridine (specifically 6-Acetyl-2,3,4,5-tetrahydropyridine [ATHP/ACTPY] and 2-acetyl-1-pyrroline [ACPY] [1], which are classified as ketones [2]) are commonly attributed to the mousy, urine (in high amounts) cheerios (in low amounts), breakfast cereal, or more generically, cracker biscuit flavor in sour beers. The flavor is detected towards the end of the swallow. The exact cause of this perceived flavor is not definitive. Diacetyl has also been indicated as a potential cause to this flavor in sour beers. However, Tetrahydropyridine seems to be the most likely cause. The flavor tends to age out of sour beers, although the exact mechanism for this is not fully understood [3]. Michael Tonsmeire also noticed that pitching rehydrated wine yeast at bottling reduces the amount/duration of this flavor [4].
In food, Tetrahydropyridine is associated with the aroma of baked goods such as white bread, popcorn, and tortillas, and is formed by Maillard reactions during heating. ATHP and ACPY have an odor threshold of 0.06ng/l [1].
Traditionally, the mousy/cheerios flavor from THP is considered an off flavor in both wine and sour beer. There is some debate and differing opinions as to whether or not a small amount of THP flavor is allowable (or even enjoyable) in sour beers, however most consider any level to be an off flavor.
Production
Editor's note: special thanks to ne0t0ky0 on Homebrewtalk for collecting some of these resources.
Brettanomyces, Lactobacillus, and Pediococcus can produce forms of Tetrahydropyridine. In Brettanomyces, 2-acetyl-3,4,5,6-tetrahydropyridine (ATHP/ACTPY) can be metabolized by the amino acid L-Lysine and ethanol with oxygen having a stimulatory effect in it's production, although little else is known about it's production in Brettanomyces [5]. ATHP is further metabolized into 2-ethyltetrahydropyridine (ETHP/ETPY) by Brettanomyces, although not much is known about this metabolic process either [6].
Heterofermentative Lactobacillus spp. can also produce ATHP and ETHP from Lysine and ethanol [7][8][9].
Some species of Pediococcus have been associated with the production of ATHP. In particular, these include P. pentosaceus [10][11], and P. clausenii [12].
Thresholds
Editor's note: the following thresholds are from a study on wine, and may not hold true for beer.
- 2-ethyltetrahydropyridine (ETHP/ETPY)
- Taste threshold (wine): 150 µg/L
- Concentration reported in wines exhibiting mousy off-flavour: 2.7-18.7 µg/L
- 2-acetyltetrahydropyridine (/ATHP/ACTPY) -
- Odor threshold (water): 1.6 µg/L
- Concentration reported in wines exhibiting mousy off-flavour: 4.8-106 µg/L
- 2-acetyl-1-pyrroline (ACPY)
- Odor threshold (water): 0.1 µg/L
- Concentration reported in wines exhibiting mousy off-flavour: Tr-7.8 µg/L [13]
Discussions
Below is a list of discussions on internet forum threads that may shed light on specific strains and individual experiences. Keep in mind that many of the opinions and experiences are anecdotal, although commonalities and shared experiences may prove to be useful and accurate.
- Milk The Funk Thread
- Homebrewtalk thread started by "ne0t0ky0"
- Homebrewtalk thread started by "loctones", comments by Michael Tonsmeire
- Babblebelt thread with comments by Chad Yakobson
References
- ↑ 1.0 1.1 6-Acetyl-2,3,4,5-tetrahydropyridine. Wikipedia. Retrieved 3/210/2015.
- ↑ Humbard, Matt. Milk The funk Discussion. 3/10/2015.
- ↑ Tonsmeire, Michael. Homebrewtalk.com post 1. 11/21/2014. Retrieved 3/10/2015.
- ↑ Tonsmeire, Michael. Homebrewtalk.com post 2. 11/21/2014. Retrieved 3/10/2015.
- ↑ Yakobson, Chad. The Brettanomyces Project; Introduction. Retrieved 3/10/2015.
- ↑ Joseph, C.M. Lucy. Aromatic Diversity of Brettanomyces. U.C. Davis. Retrieved 3/10/2015.
- ↑ Sparrows, Jeff. Wild Brews. Brewers Publications. 2005. Pg. 112.
- ↑ Lahtinen, Ouwehand, Salminen, von Wright. Lactic Acid Bacteria: Microbiological and Functional Aspects, Fourth Edition. Pg 348.
- ↑ Heresztyn, Tamila. Formation of Substituted Tetrahydropyridines by Species of Brettanomyces and Lactobacillus Isolated from Mousy Wines.
- ↑ UniProt article. Retrieved 3/10/2015.
- ↑ UniProt article. Retrieved 3/10/2015.
- ↑ UniProt article. Retrieved 3/10/2015.
- ↑ Malolactic Fermentation 2005. Geneva on the Lake. Feb 2005. Retrieved 3/10/2015.