What is a characteristic of the bitterness contributed by beta acids when aged?

The characteristic of the bitterness contributed by beta acids when aged is that it can grow in intensity. Beta acids, which derive from hops, are not nearly as bitter as alpha acids but exhibit distinctive properties as they age. Over time, beta acids can oxidize and transform into other compounds, which can enhance their perceived bitterness or contribute to a more complex flavor profile. This process can result in a bitterness that develops more character rather than simply diminishing.

The options regarding decrease, becoming sweeter, or remaining the same don't accurately reflect the volatile nature of beta acids or the changes they undergo. Over time, instead of fading, the bitterness may actually become more pronounced and integrated into the overall flavor profile, particularly if the beer is aged under conditions that facilitate these changes.