Improving and controlling hop flavor in dry hopped bottom fermented beers by the use of activated carbon

Sensory Session
Andreas Brandl, Doemens Academy GmbH, Stefanusstr. 8, 82166 Gräfelfing, Germany
Co-author(s): Christina Schönberger, Joh. Barth und Sohn, Nürnberg, Germany; Urs Wellhoener, Boston Beer Company, Breinigsville, PA, USA

ABSTRACT: Beer flavor is very complex, being derived from components that arise from a number of sources. In bottom fermented beers the sulfur-containing components from yeast metabolism, such as hydrogen sulfide and sulfur dioxide, make a significant contribution to beer flavor, whereas in top fermented beers often the fruity and estery substances are dominant. Especially in freshly filled beers hydrogen sulfide can exceed the very low flavor threshold (5 µg/L) leading to an unpleasant off-flavor. During beer storage sulfur flavor will be degraded due to oxidative processes. Thus the sulfury notes need to be controlled in fresh beers and especially in dry-hopped beers, as the fruity hop aroma interferes with the sulfury components, which leads to an unbalanced sensory impression. An easy and pragmatic way to control hydrogen sulfide is by adding a special activated carbon as a filtering aid during filtration or lagering. Tests with non–dry-hopped beers with the addition of activated carbon showed a significant reduction in hydrogen sulfide leading to improved acceptance in sensory evaluation. In a pilot scale (5 hL) we adopted a commercial dry-hopped beer recipe and filter dry-hopped bottom fermented beers with and without activated carbon to determine the flavor impact on the final product. The beers were controlled by sensory evaluation, and the hydrogen sulfide level was measured, as well as the concentration of hop aroma substances. The aim was to emphasize the characteristic hop derived spicy and fruity notes coming from the dry-hopping resulting in a more balanced beer even in fresh conditions.

Andreas Brandl studied brewing and beverage technology at TU Munich-Weihenstephan. From 2001 to 2005 he worked on his Ph.D. thesis on the implementation of PCR-based methods in brewery quality assurance. In 2005 he began employment as a project engineer for aseptic filling lines at Krones AG, and in 2007 he changed to the Bitburg Brewery Group as head of the brewery pilot plant. In Bitburg he was responsible for the organization and documentation of brewing technology trials. Since 2010 he has been working for the Doemens Academy as head of the microbiology lab and consultant in brewing technology.