are molecules containing one or more aromatic rings and two or more hydroxyl (OH) groups attached to aromatic rings. The polyphenols found in beer include simple polyphenols (two or more hydroxy groups on a single aromatic ring) or multiple ring structures such as the proanthocyanidins, which, in turn, may include catechin, epicatechin, and gallocatechin, as well as various polymers constructed from them. Polyphenols are derived directly from malt and hops and are often involved in haze formation in finished beer. See chill haze, colloidal haze, and haze. They have no aroma, and their major gustatory impact is a perception of astringency. Astringency is not technically a taste sensation, that is, it is not perceived by the taste buds. Rather, it is a so-called chemesthetic sensation, which is essentially tactile, because it is perceived by the trigeminal nerve. Chemically, this astringency is the result of polyphenols combining with proline-rich proteins in our saliva to form insoluble complexes. Usually, proteins in the mouth perform a lubricating function on the mouth’s surfaces. When polyphenols rob the palate of lubrication, the mouth feels rough and a mouth-puckering sensation is perceived. Whereas astringency from tannin can be considered a positive aspect of some wines, polyphenol astringency in beer tends to clash with hop bitterness and is rarely appreciated.