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→Other Flavor and Non-flavor Compounds
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" />.
In general, lower storage temperatures preserve hop compounds. Cans also help preserve some hop compounds versus bottles because bottle caps can strip certain hop compounds such as myrcene and caryophyllene when stored at room temperature (less so when stored cold). For example, one study found a moderate amount of degradation of humulinones, iso-α-acids, and residual α-acids when dry hopped beers were stored at 20°C versus 3°C. There was also an overall decrease in hop aroma compounds during warm storage, with some esters, hop monoterpenes, and sesquiterpenes showing poor storage stability compared to other ester compounds, monoterpene alcohols, and ketones which increased during warm storage. After 10 months of storage, the dry hopped beers stored at 20°C had a significant drop in floral, citrus and tropical fruit notes when compared to the same beers stored at 3°C <ref>[https://onlinelibrary.wiley.com/doi/full/10.1002/jib.667 Kemp, O., Hofmann, S., Braumann, I., Jensen, S., Fenton, A., and Oladokun, O. (2021) Changes in key hop-derived compounds and their impact on perceived dry-hop flavour in beers after storage at cold and ambient temperature. J. Inst. Brew., https://doi.org/10.1002/jib.667.]</ref>.
[[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.