13,602
edits
Changes
no edit summary
Polyphenols generally contribute to an astringent taste in beer, and this can be intensified at a lower pH (4-4.2). Oxidation of polyphenols might make them more astringent depending on the degree of "polymerization degree" (see [https://winemakermag.com/1045-tannin-chemistry-techniques this article]), although residual sugars reduce their astringency. Sensory analysis of lagers has shown that aged lagers became less bitter and more astringent over time (especially at a higher temperature or a higher pH), probably due to a decrease in IBU's and bitter polyphenols like catechin, and an increase in oxidized polyphenols <ref name="Callemien_2010" />.
Heavier polyphenols such as procyanidin and prodelphinidin also contribute to beer haze after packaging. See (see [[Aging_and_Storage#Haze|Haze]] above) and darkening in color after packaging. While beer darkening is also caused by oxygen and storage at higher temperatures, and possibly also by slow Malliard reactions, yellow-brown pigments can also come from oxidized polyphenols. The catechin polyphenol from hops can oxidize into yellow pigments such as dehydrodicatechin . This oxidative reaction occurs more so at a pH of 6 rather than at a pH of 3, and is greatly inhibited by storing beer cold. These reactions have been studied more so in wine and port; anthocyanidins bind with flavanols or acetoacetic acid, producing yellow-brown pigments. Pyruvic acid, vinylphenol, cinnamic acid, glyoxylic acid, ad furfural derivatives have also been identified as precursors to yellow-brown pigmentation in wine <ref name="Callemien_2010" />.
====Tannic Acid====