Analysis of polysaccharide and proteinaceous macromolecules in beer using asymmetrical flow field-flow fractionation

摘要

This paper demonstrates the potential of asymmetrical flow field flow fractionation coupled with online multi-angle light scattering, differential refractive index and UV detection for the fractionation and analysis of macromolecules in beer regarding their composition, molar mass (M) and relative concentration. The macromolecules in the liquid and foam of two types of beer, light lager and porter, were analysed in their native state with minimal sample preparation. The results showed the presence of three major populations of macromolecules. In lager beer liquid, the early eluting population has an average M of 2 × 10~4 g/mol and an intense UV absorbance at 280 nm suggesting the presence of proteinaceous macromolecules. The second and the third populations, which elute at consecutively longer retention times, have M ranging from 10~5 to 10~7 g/mol. They are not UV-active at 280 nm, suggesting the elution of polysaccharides. The second population was identified as β-glucans as a result of β-glucanase treatment. The third population was not identified in the present study. The results show that similar populations are present in lager beer foam and that the macromolecules appear to be present in a more aggregated state. The M range of macromolecules in porter beer liquid ranged from 10~5 to 10~8 g/mol. A fraction of macromolecules eluting at longer retention times is highly UV-active, which shows that there are great variations in the macromolecular profile of lager and porter beer.