APPLICATIONS OF FAST PROTEIN LIQUID-CHROMATOGRAPHY (FPLC) TO THE ANALYSIS OF THE NITROGENOUS CONSTITUENTS OF BEER

The nitrogenous constituents of beer were investigated by several Fast Protein Liquid Chromatography (FPLC) techniques. Size exclusion chromatography of dialysed beer material using columns of Superose 6 and Superose 12 suggested that beer polypeptide material was distributed across a wide relative molecular mass (Mr) range with discrete fractions of high Mr (Mr 300 000, Mr 500 000), Mr c60 000, Mr c40 000 and relatively low Mr (Mr 5 000-20 000). The composition of fractions Mr > 40 000 and Mr 40 000-60 000 was investigated by ion exchange chromatography. Differences were detected in the elution profiles of fractions prepared from beers brewed from grists comprising 100% malt, 80% malt plus 20% torrfied wheat and 100% malted wheat consistent with differences in the polypeptide composition of these fractions. The Superose 12 column, although designed for the fractionation of high molecular weight components, also provided a method of fractionating low molecular weight nitrogenous materials directly from beer (for example fractions containing purine nucleosides). Reverse phase chromatography was employed in the analysis of beer peptides and demonstrated the complex composition of beer peptide fractions.