Daniele Stock Leh (1), Thomas Becker (1), Martina Gastl (1); (1) Technische Universität München, Freising, Germany
Cell walls of barley are made, in major part, of beta-glucans, which are viscous at a high molecular weight. A poor degradation could lead to processing problems in the brewery, like slow lautering performance and filtration, as well as haze formation in beer. During the malting process, barley cell walls are degraded to smaller molecules by a group of beta-glucanases, synthesized during grain germination, and which have a specific acting mode. Besides enzymatic development, cell wall properties, like microstructure, can slow down cytolysis by substrate inhibition. The microstructure is variable between barley cultivars. In Germany, new winter cultivars are being developed with improved malting quality, but their cytolysis capacity is still under optima compared to new spring cultivars. Understanding how cell walls in different varieties re degraded and how the different enzymes responsible for this degradation act could be of great interest for breeders and brewers. Methods to determine total beta-glucanases activity are well stablished, but there is a lack of methods to determine the activity of the specific enzymes that actuate barley cell wall degradation during malting. In this work, different barley varieties were evaluated, using a LC-MS/MS method for oligosaccharide determination. The beta-glucan degradation was followed during mashing in different mashing programs, indicating how they are degraded in the brewing process and the mode of action of beta-glucanases. The results can clarify how cytolysis could be enhanced in barley breeding programs to optimize processability.
Daniele Stock Leh completed her B.S. degree in chemistry at Universidade Estadual do Centro-Oeste, Brazil. In 2013 she obtained her M.S. degree in organic chemistry at Universidade Federal do Paraná, Brazil. In the same year she began her Ph.D. thesis at Technische Universität München, in the Institute of Brewing and Beverage Technology. The aim of her research is to understand the role of substrate structure and enzymatic development for cytolysis during the malting process.