Martina Gastl (1), Thomas Becker (1), Benedikt Meier (1), Christoph Neugrodda (1); (1) Technische Universität München-Weihenstephan Lerhstuhl für Brau- und Getränketechnologie, Freising, Germany


This work examines the influence of crude protein content, as well as malt modification, on beer quality. Three barley samples (different protein content, same variety) were malted to get samples with high, medium and low soluble nitrogen levels (according to Congress mash). Standardized beers were produced from these highly, moderately and lowly modified malts. The resulting beer quality aspects were evaluated in terms of foam stability, flavor stability, and especially colloidal stability. The colloidal stability of the beers was examined in a forcing test. In addition to the established scattered light measurement, turbidity was surveyed with recording of the particle size distribution of the haze particles with laser diffraction and use of optical examination methods to analyze the morphology of the haze particles. In consequence, the results point out that evaluation only of barley/barley malt according to the (crude) protein content is not practical, since the composition of soluble barley or malt proteins (molecular size, isoelectric point, ratio) has an impact on beer quality. Therefore, soluble nitrogen is proposed as an appropriate parameter to influence beer quality.

Martina Gastl apprenticed as a brewer and maltster from 1994 to 1996 in Klosterbrauerei Andechs, Germany. She studied brewing and beverage technology at the Technische Universität München-Weihenstephan, Germany. She graduated as an engineer in 2002. From 2002 until 2006 she completed her Ph.D. degree concerning “Technological Influence on Lipid Degradation in Terms of Improvement of Beer Flavour Stability.” She is currently assistant professor and head of the research group Raw Materials Based Brewing and Beverage Technology at the Lehrstuhl für Brau- und Getränketechnologie in Weihenstephan. She is working on her postdoctoral lecture qualification; her research interest involves characterization and interaction of flavor-active taste and aroma compounds in cereal-based beverages influencing beverage harmony.