The Gel Filtration Chromatographic-Profiles
of Proteins and Peptides of Wort and Beer:
Effects of Processing - Malting, Mashing,
Kettle Boiling, Fermentation and Filtering

A.M. Osman ¹, S.M. Coverdale ¹, K. Onley-Watson ¹, D. Bell ² and P. Healy ^2
1Leslie Research Centre, Farming Systems Institute, Agency for Food and Fibre Sciences, QDPI, Toowoomba, QLD 4350, Australia.
²Castlemaine Perkins Brewery, Milton, Brisbane, QLD 4007, Australia.

J. Inst. Brew. 109(1), 41-50, 2003  |   VIEW ARTICLE

ABSTRACT
Barley and malt proteins, of infusion (IoB) and decoction (EBC) mashing worts as well as commercial wort and beer, obtained from the Castlemaine Perkins brewery, Brisbane, were gel filtered, with or without further treatments. A general, similar pattern of protein and peptide profiles emerged from barley malt and beer. This confirmed the widely assumed fact that beer proteins descend from barley, some transformed and others perhaps mostly unchanged by processing. In the gel-filtrate profiles, a maximum of 8 or 9 fractions were discerned. These fractions were collected and quantified for protein contents and amino acid compositions. The first four fractions contained the proteins and polypeptides of molecular weight higher than 14,000. Consequently, the remaining fractions contain the smaller peptides (<14,000), that were completely removed by dialysis. The effects of processing on proteins and peptides varied contingent upon the type of processing step considered and the pre-chromatographic treatment. Malting was the most effective process remarkably increasing the soluble protein contents, especially the smaller peptide fractions and the colour development. This is the first report, as far as we are aware of, on the gel filtration profiles of wort and beer low molecular weight peptides including those of barley wort. The importance of the smaller peptides in foam formation and retention cannot be overemphasised. The amino acid composition of the fractions revealed much more diversity than was observed in the comparison of the profiles. Proline content of fraction 1 resembled that of barley soluble proteins while fractions F2, F3 and F4 that of glutelin and only fraction 8 that of hordein. The latter, suggests that hordeins or, at least the peptide products rich in proline, are likely to be completely digested to amino acids, during malting.

Key words:
Amino acids, barley, beer, protein and peptide-profiles, wort.

Publication no. G-2003-0306-090  ^©2003 The Institute & Guild of Brewing