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

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.

Barley and Malt Proteins and Proteinases: II. The Purification and Characterisation of Five Malt Endoproteases, Using the Highly Degradable Barley Protein Fraction (HDBPF) Substrate

“…This suggests that each enzyme specifically hydrolysed different peptide bonds formed by different amino acid combinations. It is pertinent to note that the profiles of some of these peptides are very similar to the beer peptide profiles reported previously 15 . The beer peptides develop mainly during malting and, presumably, as the result of the endoproteolytic action of malt endoproteases.…”

A Rapid Method for the Recovery, Quantification and Electrophoretic Analysis of Proteins from Beer

“…Proteins and their derivatives play a key role in determining beer quality; indeed these molecules affect colour, flavour, foam formation and retention, mouthfeel, and the colloidal stability of beer thus determining the shelf-life of the product 11 . Even if there are different schools of thought on the role played by proteins in beer, there is general agreement on the fact that specific polypeptides can determine some specific "qualities" -in the broadest sense of the word -of the beverage.…”

“…This has been done by using methods exploiting techniques such as gel filtration 11 or sensitivity to (NH 4 ) 2 SO 4 precipitation 4 . Unfortunately these procedures are cumbersome and time-consuming.…”

Barley and Malt Proteins and Proteinases: I. Highly Degradable Barley Protein Fraction (HDBPF), a Suitable Substrate for Malt Endoprotease Assay

“…This has to be worked out for each extract to avoid opaqueness in the reaction medium. Often in the literature the protein fraction degraded during malting or natural germination is described as the hordein fraction 6,12,14,15 . The amino acid composition of HDBPF indicates that it is not a typical hordein with the usual high proline (>50%) or glutamic acid plus glutamine content 11 .…”