Identification of the Major Proteins in Beer Foam by Mass Spectrometry following Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis

Previously unknown beer and beer foam proteins of barley origin were identified by tandem mass spectrometry (MS) sequencing after in-gel tryptic digestion. Coomassie blue stained sodium dodecyl sulfate-polyacrylamide gel electrophoresis 40-kDa and 7- to 17-kDa bands were excised for these analyses. In total, there were 30 proteins detected, 21 proteins found in beer, and 24 proteins found in beer foam including the common 15 proteins in beer and 2× foam. Most originated from the barley albumins and were resistant to enzymes during brewing. There were also two hordein-related proteins. The proteins identified enlarge and update the list of proteins related to foam, usually confined to protein Z4, lipid transfer protein 1 (LTP1), and some hordein-derived proteins.