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

Abstract

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). Watersoluble 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 watersoluble 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.

Proteomics as a tool to understand the complexity of beer

“…Intact protein analysis has been used to study glycation of low molecular weight barley proteins occurring during the malting process (Bobalova & Chmelik, 2007;Lastovickova, Mazanec, Benkovska, & Bobal'ova, 2011). The final malts were noted to demonstrate marked differences in the presence of glycated forms of the proteins with LTP1 being modified by up to four hexose additions.…”

Beer fingerprinting by Matrix-Assisted Laser Desorption-Ionisation-Time of Flight Mass Spectrometry

“…The detected protein molecular masses correspond to those obtained from beer or malt using MALDI-TOF-MS by other authors employing protein precipitation (Bobálová et al, 2008;Lastovičková et al, 2010) or Divergent Flow Isoelectric Focusing separation (Mazanec et al, 2009) prior to the MALDI-TOF-MS analysis. The major signal at m/z 9.69 kDa was attributed to the molecular ions of LTP1 (theoretical MW = 9695 Da) and the molecular ions with masses increased by increments of 162 Da corresponded to its glycosylated forms.…”

125th Anniversary Review: The Non-Biological Instability of Beer

“…It is also understood that proteins associated with carbohydrates are important for foaming 24,115 . Carbohydrate moieties attached to polypeptides lower the extent to which foaming polypeptides such as LTP are lost through the brewing process 85 . Polypeptides derived from wheat appear to have superior physicochemical properties as pertains to foaming 79 .…”