13,594
edits
Changes
added Maillard reactions to "Other Flavor and Non-flavor Compounds"
Many other compounds increase or diminish over time in packaged beer. Cyclic acetals (2,4,5-trimethyl-1,3-dioxolane, 2-isopro-pyl-4,5-dimethyl-1,3-dioxolane, 2-isobutyl-4,5-dimethyl-1,3-dioxolane and 2-sec-butyl-4,5-dimethyl-1,3-dioxo-lane) in packaged beer that has been in contact with oxygen. Heteroclyclic compounds (furan, furfural, and furanone based compounds) increase regardless of oxygen exposure but generally remain far below flavor threshold, however, their presence correlates with stale flavors in sensory tests and can thus serve as indicators for stale beer. Pyrazines such as pyrazine, 2-ethyl-6-methylpyrazine, 2-ethyl-5-methylpyrazine, 2-acetylpyrazine, 2,3-dimethylpyrazine, 2,5-dimethylpyrazine, 2-ethyl-3,6-dimethylpyrazine, 2-ethyl-3,5-dimethylpyrazine diminish over time in packaged beer <ref name="Vanderhaegen_2006" />.
Products of Maillard reactions, which include a diverse range of reactions, have also been found in beer, although research in this area is limited. Some Maillard compounds found in aging beer remain under taste threshold, for example, furfural and 5-hydroxymethyl furfural. It is hypothesized that a wide range of unknown Maillard reactions and their intermediates might play a role in the aging of beer. In particular, the bready, sweet, caramel and wine-like character of stale beer might be due to Maillard reactions <ref name="Vanderhaegen_2006" />.
[[Tetrahydropyridine]] (THP) is a compound that tastes like Cheerios® or corn tortilla chips that often develops soon after packaging beers that contain ''Brettanomyces'' or heterofermentative ''Lactobacillus''. It is usually detected after swallowing the beer. This compound is stimulated by oxygen, and often ages out after a few months. See the [[Tetrahydropyridine]] page for more information.