Proteins in raw materials play an important part in both malting and brewing processes, as actors of raw material biotransformation, contributors to foam, haze or even nitrogen source for the yeast. Nonetheless, a comparable total protein content of barley can lead to various malt qualities and different proteolysis levels. In a context of climate change, of inputs reduction and need of more sustainable raw materials, there is a need to improve knowledge of proteins in barley. The collaborative "PROsIT" project (barley PROteins of InTerest) proposed to draw up the qualitative profile of the different barley proteins and tried to identify the possible relation to malt quality. The project is supported by FSOV (Found to support breeding selection in France) and all barley to beer chain (CTPS, Breeders, ARVALIS, French Maltsters & Brewers) The analysis of barley protein fractions was developed on a sequential isolation inspired by Schalk et al. (2017) [1] followed by capillary electrophoresis analysis (Labchip, PERTEN). In more details, protein fractions are first isolated according to Osborne [2] classification: albumin, globulin, hordein, glutelin. Each of them are further separated according to molecular weight to collect, respectively 18,10, 10 and 15 peaks. A collection of 321 barley samples of different crops, locations, varieties and nitrogen fertilizations produced by project partners was analysed. All the samples were micro-malted at IFBM micromalting plant and malts were characterized (extract, friability, total & soluble proteins, wort viscosity & beta glucans content, diastatic power, etc.). A database of 1284 profiles (more than 16 000 peaks) and the corresponding malt parameters was built. The first data treatment indicates that there is a very large diversity of barley protein composition for the same total nitrogen content with a 2 up to 3-fold factor depending the protein fraction. In other words, several barley batches could exhibit the same protein content but contain some proteins of interest and some less useful for the maltsters or brewers. Besides, a PCA analysis on nitrogen fertilization trials on 220 samples shows an important varietal effect on protein profile. However, the crop, location or fertilizing modalities have no significant effect on protein composition in our sampling. This major result demonstrates that the barley variety is the most significant factor triggering different protein compositions. But the different clusters gather independently some 6 row winter lines can be with some 2 row spring lines. This means that the barley specie does not drive, alone, the protein profile. The data treatment needs to be completed but this work shows the importance of barley protein composition to assess malt quality. And the results gathered in the project is the beginning of a larger study investigating the proteins of interest for the barley to beer chain.
