What causes chill haze in beer?

Chill haze in beer is primarily caused by the temporary interaction between polyphenols and proteins when the beer is cooled. When beer is refrigerated, certain proteins, particularly those derived from malt, can bind with polyphenols, which are compounds commonly found in hop and malt. This interaction leads to the formation of larger molecules that can become visible, resulting in a haze.

As the temperature of the beer rises, these proteins can often re-dissolve, which may make the haze disappear. However, at cold temperatures, the haze persists, giving the beer a cloudy appearance. This phenomenon is most commonly observed in beers that are not well-fined or filtered, as these processes typically remove excess proteins and polypeptides that can contribute to haze formation.

The other options presented are not responsible for chill haze. For instance, excessive carbonation does not affect haze formation but rather impacts mouthfeel and perception of the beer. The presence of wild yeast may lead to other issues in beer stability and flavor but is not a direct cause of chill haze. Likewise, storing beer at overly cold temperatures could affect other aspects of beer quality but is not a factor that contributes to the formation of chill haze itself.