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Beer Polypeptides and Silica Gel Part II. Polypeptides Involved in Foam Formation
Author(s) -
Leiper Kenneth A.,
Stewart Graham G.,
McKeown Ian P.
Publication year - 2003
Publication title -
journal of the institute of brewing
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.523
H-Index - 51
eISSN - 2050-0416
pISSN - 0046-9750
DOI - 10.1002/j.2050-0416.2003.tb00595.x
Subject(s) - brewing , chemistry , adsorption , proline , chromatography , size exclusion chromatography , amino acid , glycoprotein , haze , biochemistry , organic chemistry , enzyme , fermentation
Beer contains approximately 500 mg/L protein depending on the brewing procedures employed. This protein is in the form of polypeptides, the majority of which lie within the 10–40 kD size range. Some of these polypeptides are responsible for causing colloidal haze, some enhance foam stability and the remainder appear to have no function in beer except to contribute to mouth‐feel. Those polypeptides involved in haze formation were described in a previous paper. To continue these studies, data is presented to show that foam polypeptides are highly glycosylated and that purified foam glycoprotein contains low levels of the amino acid proline. As silica preferentially adsorbs polypeptides rich in proline, it is unlikely to adsorb this material and damage foam stability. The molecular sizes and composition of glycoproteins recovered from untreated beer, purified foam and beer from which the foam component has been removed are presented. These fractions include the polypeptides responsible for foam stability and those that appear to have no role in physical stability.