Proteome Analysis of Metabolic Proteins (pI 4–7) in Barley (Hordeum vulgare) Malts and Initial Application in Malt Quality Discrimination

Barley malt is essential for beer production. In the present study, the nonprolamin fractions including proteins with structural functions or metabolic activities were extracted from barley malts of the widely used cultivars Gangpi and Baudin in China. The metabolic proteomes (pI 4-7) were constructed and compared using two-dimensional electrophoresis (2DE) followed by matrix-assisted laser desorption/ionization-tandem time-of-flight mass spectrometry (MALDI-TOF/TOF) identification. There were 333 and 354 spots detected in the 2DE gels of Gangpi and Baudin malts, respectively, and about 90% of these spots were shared by the two malts. For all, 377 were successfully identified to 192 proteins, most of which were enzymes and enzyme inhibitors, suggesting important roles in barley malting and the mashing stage of brewing. The Baudin malt was found to contain more spots representing amylases, pathogen-related proteins, and chaperones than the Gangpi malt. In addition, enzymes involved in glycolysis and redox pathways showed significantly different profiles between the two malts, permitting a more in-depth elucidation of the relationship between differential proteins and malt qualities.