Changes

Forms of ''Tetrahydropyridine'' (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, ''TetrahydropyridinTetrahydropyridine'' 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, ''TetrahydropyridinTetrahydropyridine'' 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 ACPY have an odor threshold of 0.06ng/l <ref name="wikipedia"></ref>.

[[Brettanomyces]], [[Lactobacillus]], and [[Pediococcus]] can produce forms of ''TetrahydropyridinTetrahydropyridine''. 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>.