2D-HPLC and MALDI-TOF/TOF analysis of barley proteins glycated during brewing.

The barley proteins have been the subject of interests of many research groups dealing with barley grains, malt and beer. The proteins which remain intact after harsh malting conditions influence the quality and flavor of beer. The characteristic feature of the proteins present in malt and beer is their extensive modification with carbohydrates, mainly glucose that comes from the starch degradation during technological processes. The degree of the protein glycation has an effect on the quality of malt and beer and on the properties of the beer foam. A combination of two-dimensional high performance liquid chromatography (2D-HPLC) and matrix assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF/TOF MS) was used for the analysis of the protein extracts that were reduced, alkylated, and degraded enzymatically without prior protein separation. This so-called "shot-gun" approach enabled us to determine glycation sites in one third of the proteins identified in the study and to propose potential glycation markers for fast and efficient monitoring during malting.