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updated Haze section
===Haze===
Also referred to as ''colloidal instability'', haze that forms in has been deemed a problem for most beer after packaging is often attributed to the interactions between polyphenols and proteins. Haze generally limits the shelf life styles for mainly aesthetic reasons, especially for lighter styles of beer. Beer contains much where haze is more haze-active proteins noticeable than haze-active polyphenolsdarker styles. Haze-active proteins While clarity is considered important for most beer styles, some beer styles are acidic hydrophilic polypeptides intended to be hazy (some German wheat beers, Belgian wheat beers, NEIPA, Abbey ales that originate from barley and are rich refermented in proline, glutamic acidthe bottle, Belgian lambic and glycosylated. Smaller phenols such as phenolic acids and flavonols do not contribute to hazederived beers, but heavier polyphenols such as procyanidin and prodelphinidin are strong haze inducersmixed fermentation beers). These proteins and polyphenols bind together to form haze Clarity in packaged beer. The polyphenol found in hops, catechin, does not is one form haze immediately but can cause haze after a period of storage. The pH of the beer has a huge impact on this reaction: much more haze is formed at a pH of 4.0 than it is at a pH of 3.0 or above 4.2. Higher ABV beers also encourage more haze formation from proteins and polyphenol reactions. This haze generally forms after a period of storage stability (called the "lag phase"); the longer this lag phasealong with flavor/aroma, color, the better the beer's colloidal and foam stability). Haze can also be induced caused by wild yeast and lactic acid bacteria, carbohydrates, binding of proteins and oxidized polyphenols, metals such as iron, oxidation, the presence of aldehydes, shaking, higher temperatureexposure to high temperatures, exposure to polyphenol-rich raw materials, light, and heavy metals 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" />. Beer contains much more haze-active proteins than haze-active polyphenols. Haze-active proteins are acidic hydrophilic polypeptides that originate from barley and are rich in proline, glutamic acid, and glycosylated. Smaller phenols such as phenolic acids and flavonols do not contribute to haze, but chill heavier oxidized polyphenols such as procyanidin and prodelphinidin are strong permanent haze inducers. These proteins and oxidized polyphenols bind together to form haze in beer <ref name="Mélotte_2008" />. The polyphenol found in hops, catechin, does not form haze immediately but can become cause haze after a period of storage. The pH of the beer has a huge impact on this reaction: much more haze is formed at a pH of 4.0 than it is at a pH of 3.0 or above 4.2. Higher ABV beers also encourage more haze formation from proteins and polyphenol reactions to cause permanent as well haze. Permanent haze from proteins and oxidized polyphenols generally form after a period of storage (called the "lag phase"); the longer this lag phase, the better the beer's colloidal stability <ref name="Callemien_2010" />.
Brewers generally remove haze by additives such as tannic acid, papain, or silica gel. Some of these additives can also remove foam forming proteins. Because of this, a chemical known as PVPP is often used because it does not remove foam forming proteins. Several products are available that contain combinations of PVPP and other compounds <ref name="Callemien_2010" />.