What effect does oxygen have if included in beer?

Oxygen has a significant impact on the stability and quality of beer, and its inclusion typically leads to accelerated spoilage. When oxygen is introduced into beer, it can promote undesirable chemical reactions that result in off-flavors, particularly the formation of stale or cardboard-like flavors due to oxidation. This process can also lead to the degradation of hop compounds, causing a loss of freshness and a decline in the overall quality of the beer.

Oxidation can negatively affect not just the flavor but also the aroma and mouthfeel, making beer less enjoyable for consumers. Typically, brewers take extensive measures to minimize oxygen exposure throughout the brewing process, from fermentation to packaging and serving, in order to preserve the intended sensory characteristics of the beer.

While some brewers may aim for certain oxidized flavors in well-aged beers or specific styles, the general impact of oxygen on most beers is detrimental, leading to a shorter shelf life and a decline in product integrity.