Affinity of Proanthocyanidins and Their Oxidation Products for Haze-forming Proteins of Beer and the Formation of Chill Haze

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Amongthe polyphenols found in beer, proanthocyanidins were found to have a specific affinity for the haze-forming proteins in beer and retained their capacity to form a chill haze. Proanthocyanidins pentamer and tetramer had the highest affinities for the haze-forming proteins, followed by the trimer, dimer and catechins. During the brewing process, proanthocyanidin trimer and polymeric proanthocyanidins easily formed insoluble complexes with proteins in the wort as a result of their high affinity for proteins; consequently, these were not found in finished beer, whereas such proanthocyanidin dimers as procyanidin B₃, and catechin survived in finished beer. Procyanidin B₃ and catechin, when stored in beer or a buffer solution, seemed to undergo oxidative polymerization and increased their affinity for the haze-forming proteins to form a extensive chill haze.