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Tetrahydropyridine

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=Introduction=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>.
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 [http://www.homebrewtalk.com/f127/brett-strain-production-athp-449852/ ne0t0ky0] on Homebrewtalk for collecting some of these resources.''
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==
''Editor's note: the following thresholds are from a study on wine, and may not hold true for beer.''
** 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==
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]
* [http://www.babblebelt.com/newboard/thread.html?tid=1108752780&th=1277680358 Babblebelt thread with comments by Chad Yakobson]
==References==
<references/>
 
[[Category:Compounds]]
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