What flavors are indicative of oxidation in beer?

The presence of papery, wet, or cardboard flavors in beer is a clear indicator of oxidation. When beer oxidizes, oxygen interacts with various compounds in the beer, resulting in the formation of compounds that produce these undesirable flavors. This process can alter the beer's original character, affecting its freshness and overall taste profile.

Oxidation is often regarded as a flaw because it can detract from the intended flavors and aromas, leading to a less enjoyable drinking experience. This is particularly common in styles that are intended to be consumed fresh, such as IPAs or pale ales, where hop character and bright flavors are prominent. When oxidation occurs, these lively notes can give way to the stale, flat characteristics characterized by the papery or cardboard-like flavor.

In contrast, fruity and floral flavors might suggest a fresh hop character or yeast-derived esters without the influence of oxidation. Sweet and malty flavors can be part of a beer's intended profile, especially in certain styles, while bitter and hoppy flavors are usually desirable traits in hop-forward beers. Therefore, the presence of papery, wet, or cardboard flavors clearly stands out as a signature of oxidative damage in beer.