Christoph Neugrodda (1), Thomas Becker (1), Martina Gastl (1); (1) Chair of Brewing and Beverage Technology, Technische Universität München, Freising, Germany

Technical Session 12: Filtration
Tuesday, August 16  •  8:15–9:30 a.m.
Plaza Building, Concourse Level, Governor’s Square 14

This study dealt with one of the biggest problems and challenges of dry-hopped beers: turbidity. The use of dry-hopping allows the brewer to produce desired flavor-rich (i.e., aroma and taste) beers, but these often come with a noticeably undesirable turbidity. Brewers who produce dry-hopped beers deal with quality problems, such as high turbidity, which increases upon storage. Different stabilization methods are available and often used by brewers to decrease beer turbidity; however, when applied, some desired compounds (e.g., aroma or polyphenols) are removed. As a result, the characteristic advantages of dry-hopping are lost. To date, the filtration and stabilization methods used to control the turbidity of dry-hopped beers have not been thoroughly investigated. The aim of this project is to determine the influence of the different filtration and stabilization methods on the turbidity of dry-hopped beers, the beer foam stability and the aroma profile. To do this, the aroma profile of the beers, before and after filtration, was evaluated instrumentally and by trained panelist. In this project a base dry-hopped beer was produced, and this was then treated with different filtration and stabilization technologies. In total 19 dry-hopped experimental beers were produced using different filtration systems (separator, cartridge filter, layer filtration), different stabilization methods (PVPP and silica gel) and a combination of filtration and stabilization technologies. Different analytical methods were used to quantify the nitrogen compounds (e.g., protein profile), total polyphenols, tannoids, anthocyanogens and bitter substances in the produced beers. Haze formation was monitored in the fresh beers over a period of 20 weeks (storage at 4°C). The beer aroma profile was instrumentally quantified (GC-FID), and the sensory evaluation of the beers was carried out using two evaluation schemes. The collected data show that the use of filtration and stabilization have a noticeable impact on the quality of dry-hopped beers. It depends, however, on the selected filtration method and stabilization agent. All tested methods were able to decrease turbidity in dry-hopped beers. Some of the tested methods had a negative influence on foam stability and/or sensory evaluation. In this study, it was possible to determine the method of choice to control the turbidity in dry-hopped beers and still deliver a desirable beer quality.

Christoph Neugrodda was born in Trier, Germany. After completing his military service in 2003, he began an apprenticeship as a brewer and maltster at the Bitburger brewery in Bitburg, Germany. He successfully completed his apprenticeship, as the best in his class, in February 2006. He then started working as a full-time brewer in the Bitburger brewery. In October 2006 he started studying brewing and beverage technology at the Technische Universität München-Weihenstephan, Germany. He graduated as an engineer with a Dipl.-Ing. degree in 2012. His diploma thesis focused on the characterization of hop proteins. This project was funded by the Barth Haas Grant and was then granted the Nienaber Prize in 2013. Since April 2012 he has been working as a scientific employee at the Institute for Brewing and Beverage Technology in Weihenstephan. Beer foam is the focus of his research, and he also contributes to the innovative research projects happening at the research brewery in Weihenstephan.