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=Introduction=
Forms of ''Tetrahydropyridin'' (specifically 6-Acetyl-2,3,4,5-tetrahydropyridine (ATHP/ACTPY) and 2-acetyl-1-pyrroline (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>) are commonly attributed to the ''mousy'', ''urine'' (in high amounts) ''cheerios'' (in low amounts), or more generically, ''cracker biscuit'' flavor in sour beers. The exact cause of this perceived flavor is not definitive. However, ''Tetrahydropyridin'' seems to be the most likely cause. Dimethyl Sulfide has also been indicated as a potential cause to this flavor in sour beers, probably due to the similar ''popcorn'' flavor that DMS can provide. 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, ''Tetrahydropyridin'' is associated with the aroma of baked goods such as white bread, popcorn, and tortillas, and is formed by Maillard reactions during heating. 2-acetyl-3,4,5,6-tetrahydropyridine (ATHP) and 2-acetyl-1-pyrroline have an odor threshold of 0.06ng/l <ref name="wikipedia"></ref>.
=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.''
[[Brettanomyces]], [[Lactobacillus]], and [[Pediococcus]] can produce forms of ''Tetrahydropyridin''. 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 <ref>[http://www.brettanomycesproject.com/dissertation/introduction/ Yakobson, Chad. The Brettanomyces Project; Introduction. Retrieved 3/10/2015.]</ref>. ATHP is further metabolized into 2-ethyltetrahydropyridine (ETHP/ETPY) by Brettanomyces, although not much is known about this process either <ref>[http://ucce.ucdavis.edu/files/repositoryfiles/Joseph_5_Aromatic_Diverswity_of_Brettanomyces-82350.ppt Joseph, C.M. Lucy. ''Aromatic Diversity of Brettanomyces''. U.C. Davis. Retrieved 3/10/2015.]</ref>.
Heterofermentative [[Lactobacillus]] spp. can also produce ATHP and ETHP from Lysine and ethanol<ref>Sparrows, Jeff. ''Wild Brews''. Brewers Publications. 2005. Pg. 112.</ref><ref>[https://books.google.com/books?id=tFjsAuo5WocC&pg=PA348&lpg=PA348&dq=lactobacillus+Tetrahydropyridine&source=bl&ots=QUVyoFtIwK&sig=h1cdjB0r1pIRX2Bms8wVA0UiLk4&hl=en&sa=X&ei=4DX_VPz5CsH6oQSAzoGgBA&ved=0CEwQ6AEwCQ#v=onepage&q=lactobacillus%20Tetrahydropyridine&f=false Lahtinen, Ouwehand, Salminen, von Wright. Lactic Acid Bacteria: Microbiological and Functional Aspects, Fourth Edition. Pg 348.]</ref><ref>[http://ajevonline.org/content/37/2/127.short Heresztyn, Tamila. Formation of Substituted Tetrahydropyridines by Species of Brettanomyces and Lactobacillus Isolated from Mousy Wines.]</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=
* 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 <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>
=References=
<references/>
[[Category:Compounds]]
Forms of ''Tetrahydropyridin'' (specifically 6-Acetyl-2,3,4,5-tetrahydropyridine (ATHP/ACTPY) and 2-acetyl-1-pyrroline (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>) are commonly attributed to the ''mousy'', ''urine'' (in high amounts) ''cheerios'' (in low amounts), or more generically, ''cracker biscuit'' flavor in sour beers. The exact cause of this perceived flavor is not definitive. However, ''Tetrahydropyridin'' seems to be the most likely cause. Dimethyl Sulfide has also been indicated as a potential cause to this flavor in sour beers, probably due to the similar ''popcorn'' flavor that DMS can provide. 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, ''Tetrahydropyridin'' is associated with the aroma of baked goods such as white bread, popcorn, and tortillas, and is formed by Maillard reactions during heating. 2-acetyl-3,4,5,6-tetrahydropyridine (ATHP) and 2-acetyl-1-pyrroline have an odor threshold of 0.06ng/l <ref name="wikipedia"></ref>.
=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.''
[[Brettanomyces]], [[Lactobacillus]], and [[Pediococcus]] can produce forms of ''Tetrahydropyridin''. 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 <ref>[http://www.brettanomycesproject.com/dissertation/introduction/ Yakobson, Chad. The Brettanomyces Project; Introduction. Retrieved 3/10/2015.]</ref>. ATHP is further metabolized into 2-ethyltetrahydropyridine (ETHP/ETPY) by Brettanomyces, although not much is known about this process either <ref>[http://ucce.ucdavis.edu/files/repositoryfiles/Joseph_5_Aromatic_Diverswity_of_Brettanomyces-82350.ppt Joseph, C.M. Lucy. ''Aromatic Diversity of Brettanomyces''. U.C. Davis. Retrieved 3/10/2015.]</ref>.
Heterofermentative [[Lactobacillus]] spp. can also produce ATHP and ETHP from Lysine and ethanol<ref>Sparrows, Jeff. ''Wild Brews''. Brewers Publications. 2005. Pg. 112.</ref><ref>[https://books.google.com/books?id=tFjsAuo5WocC&pg=PA348&lpg=PA348&dq=lactobacillus+Tetrahydropyridine&source=bl&ots=QUVyoFtIwK&sig=h1cdjB0r1pIRX2Bms8wVA0UiLk4&hl=en&sa=X&ei=4DX_VPz5CsH6oQSAzoGgBA&ved=0CEwQ6AEwCQ#v=onepage&q=lactobacillus%20Tetrahydropyridine&f=false Lahtinen, Ouwehand, Salminen, von Wright. Lactic Acid Bacteria: Microbiological and Functional Aspects, Fourth Edition. Pg 348.]</ref><ref>[http://ajevonline.org/content/37/2/127.short Heresztyn, Tamila. Formation of Substituted Tetrahydropyridines by Species of Brettanomyces and Lactobacillus Isolated from Mousy Wines.]</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=
* 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 <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>
=References=
<references/>
[[Category:Compounds]]