Changes

Some volatile esters that give the beer a fruity flavor, such as isoamyl acetate that gives the beer a banana flavor, can decrease to levels below their flavor thresholds over time in packaged beer. Other volatile esters such as ethyl 3-methyl-butyrate (derived from oxidized alpha and beta acids in hops and contributes a wine-like character <ref name="williams_wagner_1979">[https://www.asbcnet.org/publications/journal/vol/Abstracts/37-03.htm Contribution of Hop Bitter Substances to Beer Staling Mechanisms. Williams and Wagner 1979.]</ref>), ethyl 2-methyl-butyrate (derived from oxidized alpha and beta acids in hops and contributes a wine-like character <ref name="williams_wagner_1979" />), ethyl 2-methyl-propionate, ethyl nicotinate, diethyl succinate, ethyl lactate, ethyl phenylacetate, ethyl formate, ethyl furoate and ethyl cinnamate (fruity, sweet character) are formed during beer aging. Lactones, which are cyclic esters, such as the peach-like hexalactone and nonalactone tend to increase during beer storage and have a significant impact on the flavor of aged beer <ref name="Vanderhaegen_2006" />. See also [[Hops#Esters|Esters From Hops]].