Changes

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" />.

====Tannic Acid====