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Abstract 055

Beer clarity stability

Proceedings, 6th Scientific and Technical Convention, Institute of Brewing, Central & Southern African Section, Durban, South Africa, 1997 pp. 67-74

K. J. Siebert

The nature of proteins and polyphenols that combine to form haze and their interactions were considered. Experiments were carried out with adsorbents to elucidate their mechanisms of action. Bentonite removes protein from beverages under a wide range of conditions, but is undesirable for stabilizing beer because it takes out foam-active protein. Silica gel is specific for haze-active protein and has remarkably little effect on foam-active protein because it binds to the same site in haze-active proteins as the polyphenols. Silica gel becomes ineffective in situations where the level of haze-active polyphenol is high because access by the adsorbent to the binding sites is partially blocked by bound polyphenols. Polyvinylpolypyrrolidone (PVPP) is more effective in removing haze-active polyphenol in situations where the ratio of protein to polyphenol is low. When there is excess protein (typically the case in beer), most of the haze-active polyphenol molecules are attached to one or more protein molecules. This hinders the binding of polyphenols to PVPP.

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