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===Haze===
Also referred to as ''colloidal instability'', haze has been deemed a problem for most beer styles for mainly aesthetic reasons, especially for lighter styles of beer where haze is more noticeable than darker styles. While clarity is considered important for most beer styles, some beer styles are intended to be hazy (some German wheat beers, Belgian wheat beers, NEIPA, Abbey ales that are refermented in the bottle, some Belgian lambic and derived beers, and some mixed fermentation beers). Clarity in packaged beer is one form of beer stability (along with flavor/aroma, color, and foam stability). Haze can be caused by wild yeast and lactic acid bacteria, carbohydrates, binding of proteins and oxidized polyphenols, metals such as iron, oxidation, aldehydes, shaking, exposure to high temperatures, exposure to polyphenol-rich materials, and sunlight <ref name="Mélotte_2008">[https://www.uclouvain.be/cps/ucl/doc/inbr/documents/DeClerckChairMelotte.pdf "Measurements of Beer Collodial Stability" (Presentation). Laurent Mélotte. Sept 2008.]</ref><ref name="Callemien_2010" />.
Polyphenol-protein haze is the most common cause of haze formation after packaging. It comes in two forms: ''chill haze'' and ''permanent haze''. Chill haze (or reversible haze) is the combination of polyphenols and proteins via non-covalent bonds at colder temperatures. This haze generally goes away after the beer is warmed up again. When beer remains hazy at room temperature (specifically 20°C), chill haze becomes permanent haze <ref name="Mélotte_2008" /><ref name="Callemien_2010" />.