Probing heat-stable water-soluble proteins from barley to malt and beer

摘要

Proteins determine the quality of barley in malting and brewing end-uses. In this regard, water-soluble barley proteins play a major role on the formation, stability and texture of head foams. Our objective was to survey the barley seed proteins that could be involved in the foaming properties of beer. Therefore two-dimensional electrophoresis and mass spectrometry were combined to highlight the barley proteins that could resist to the heating treatments occurring during malting and brewing processes. As expected, from barley to malt and to beer, most of the heat-stable proteins are disulphide-rich proteins, suspected to be involved in the defence of plants against their bio-aggressors, e.g. serpin-like chymotrypsin inhibitors (protein Z), amylase and amylase-protease inhibitors and lipid transfer proteins (LTP1 and LTP2). For LTP1s, the complex pattern displayed in 2-D electrophoresis could be related to some chemical modifications already described elsewhere, such as acylation or glycation through Maillard reactions which occur on malting. Our proteomics approach allowed the identification of the numerous proteins present in beer besides the major ones that were described so far. The involvement of these proteins in the quality of beer foam could now be evaluated.