Utilization of the Linear Mode of MALDI-TOF Mass Spectrometry in the Study of Glycation During the Malting Process

J. Inst. Brew. 116(3), 245-250,2010 The process of glycation during the malting process was monitored by the linear mode of matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS). Water-soluble proteins were investigated and two hulled barley varieties, Jersey and Tolar, were compared to the hulless line KM 1910. The crude extracts of the proteins obtained from the grain, the malt, and aliquots collected every 24 h during the malting process, were mixed with the matrix (2,6-dihydroxyacetophenone) and analyzed by mass spectrometry. The protein composition of the barley changed during the malting process. The protein patterns did not differ significantly between the three varieties of the barley grains. However, significant differences between the malts were evident. Results showed the influence of the malting process on the glycation of certain water-soluble barley proteins, nonspecific lipid transfer protein 1 (LTP1) and protein Z, of which the glycated forms survived the brewing process. These major barley proteins are very important for the formation and stability of beer foam and glycation may prevent their precipitation. Analysis results indicated that slight glycation of the proteins had occurred on the second day of malting. The linear mode of MALDI-TOF mass spectrometry was used as a fast and simple method for monitoring the patterns of low-molecular weight barley proteins with regard to barley variety discrimination. This procedure also enables the selection of barley varieties suitable for the malting industry.