Les Maîtres de l'Orge: the proteome content of your beer mug.

The beer proteome has been evaluated via prior capture with combinatorial peptide ligand libraries (ProteoMiner as well as a homemade library of reduced polydispersity) at three different pH (4.0, 7.0, and 9.3) values. Via mass spectrometry analysis of the recovered fractions, after elution of the captured populations in 4% boiling SDS, we could categorize such species in 20 different barley protein families and 2 maize proteins, the only ones that had survived the brewing process (the most abundant ones being Z-serpins and lipid transfer proteins). In addition to those, we could identify 40 unique gene products from Saccharomyces cerevisiae, one from S. bayanus and one from S. pastorianus as routinely used in the malting process for lager beer. These latter species must represent trace components, as in previous proteome investigations barely two such yeast proteins could be detected. Our protocol permits handling of very large beer volumes (liters, if needed) in a very simple and user-friendly manner and in a much reduced sample handling time. The knowledge of the residual proteome in beers might help brewers in selecting proper proteinaceous components that might enrich beer flavor and texture.