Changes

APY/ACPY (2-acetyl pyrroline) is a more volatile but more potent form of THP. It has a significantly stronger odor and lower odor threshold in wine than ATHP. It can also be found in damp pearl millet, white bread, taco shells, tortilla chips, boiled potatoes, roasted sesame seeds, pan-fired green teas, cured tobacco leaves, peanut and pumpkin seed oils, honey, several soy-based products, and more aromatic rice such as Indian Basmati. APY is primarily produced by heterofermentative LAB. In food, APY formation is due to cooking and thought to be associated with Maillard reactions, and its presence ages out quickly in food and is considered extremely volatile so much so that the food industry has created powdered forms of APY to increase the flavor stability of some foods associated with it. Some plants such as rice crops produce varying levels of APY naturally <ref name="Snowdon"></ref><ref name="Grbin_1996" /><ref name="Adams_2005">[http://pubs.acs.org/doi/abs/10.1021/cr040097y Chemistry of 2-Acetyl-1-pyrroline, 6-Acetyl-1,2,3,4-tetrahydropyridine, 2-Acetyl-2-thiazoline, and 5-Acetyl-2,3-dihydro-4H-thiazine:  Extraordinary Maillard Flavor Compounds. An Adams andNorbert and Norbert De Kimpe. 2005.]</ref>.

There have been anecdotal reports of other forms of mousy off-flavors. During the growth of lactic acid bacteria (LAB), mousy off-flavor detection fluctuated with high levels detected early on, and lower levels detected towards the end of growth. This indicates that there may be a transient, strain-dependent form of THP that can occur during malolactic fermentation. There have also been a sensory detection of mousy off-flavors at different levels than the documented levels of ATHP, ETHP, and APY, which were not associated with LAB or ''Brettanomyces'' <ref name="Snowdon"></ref>.

Sulfur-containing versions of THP exist in many vegetables and processed meats and are important aspects of their aromas. These include 2-Acetyl-2-thiazoline (the sulfur containing version of APY) and 5-Acetyl-2,3-dihydro-4 H -1,4-thiazine (the sulfur containing version of 6ATHP). These are formed in meat during processing, for example in beef and chicken broths, roasted beef, etc. They are characterized as being similar to APY and ATHP, and have a "roasty", popcorn-like odor and low thresholds. These are chemically formed during cooking and food processing and are not associated with biological metabolism or fermentation <ref name="Adams_2005" />. ===Similar Compounds===Another compound called 2-acetylpyridine, also known as 1-pyridin-2-ylethanone, is produced in malt during Maillard reactions. It is described as having a malty-biscuity, corn-chip, corn tortilla, popcorn flavor. Since it is found in malt, it is a regular contributor to the flavor of beer. This compound could easily be confused with forms of THP, but it is not considered to be a variety of THP <ref>[https://en.wikipedia.org/wiki/2-Acetylpyridine 2-Acetylpyridine. Wikipedia. Retrieved 09/04/2018.]</ref><ref>[http://www.thegoodscentscompany.com/data/rw1012221.html 1-pyridin-2-ylethanone. The Good Scents Company website. Retrieved 09/04/2018.]</ref><ref>[https://www.aroxa.com/beer/beer-flavour-standard/2-acetyl-pyridine/ 2-acetyl pyridine. Aroxa website. Retrieved 09/04/2018.]</ref>.