Proanthocyanidins in hops

Liquid chromatography-tandem mass spectrometry (LC/MSn) coupled with various two-dimensional NMR methods are among the most practical approaches for analyzing proanthocyanidins from hops. Using these and other analytical approaches, it has been shown that hops contain a preponderance of polymeric material, including proanthocyanidins which are dominant, but small quantities of prodelphinidins and propelargonidins are also present. The flavanoids (+) catechin and proanthocyanidin B3 are the most representative followed by B1, B4 and C2. The relative proportions of the various proanthocyanidins vary greatly depending on the variety and climatic conditions as shown by differences in the proanthocyanidins in the same cultivar from different geographic regions. Proanthocyanidins have received a considerable amount of attention in the brewing industry because of their tendency to complex with proteins and contribute to non-biological haze formation, but they stabilize the organoleptic properties and color, and contribute to the astringency and bitterness, which are desirable attributes. Recent studies also show that these compounds, which are classic antioxidants, may also have significant beneficial health effects. Numerous proanthocyanidins including catechin, prodelphinidin B3, procyanidin B3 and epicatechin are present in beer.