PURIFICATION AND PROPERTIES OF THE MAJOR ANTIGENIC BEER PROTEIN OF BARLEY ORIGIN

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Abstract
The major antigenic beer macromolecule, Antigen 1, has been isolated from commercial lager beer by succesive use of ultrafiltration, alcohol precipitation, anion exchange, cation exchange and gel filtration chromatography. Amino acid analyses showed a composition identical with that of a major barley albumin, Protein Z, except for a 16% lower content of lysine. Like Protein Z, Antigen 1 showed a molecular weight (MW) near 40,000 in gel filtration and SDS-gel electrophoresis. Unlike Protein Z, Antigen 1 contained 2·5% carbohydrate and was more acidic. When properly standardised, the amount of Antigen 1 in beer could be determined immunoelectrophoretically. Contents ranged from 22 mg/litre in a pale ale (7·7°P; 36% brewers adjunct) to 170mg/litre in a stout (18·8°P). The results suggest that Antigen 1 may account for more than 10% of the total non-dialysable proteinaceous material in beer, and that about 25% of the Protein Z present in the brewing materials may be recovered with an almost unmodified protein structure as Antigen 1 of beer. Apparently, Antigen 1 was not affected by stabilisation of the beer with insoluble PVP or with papaya proteinases.