C. NEUGRODDA (1), M. Gastl (1), T. Becker (1);
(1) TUM – Lehrstuhl für Brau- und Getränketechnologie, Freising, Germany
Technical Session 5 - Foam
Monday, June 15
10:45 a.m.–12:00 p.m.
Besides turbidity, beer foam is one of the most important quality parameters of beer. The consumer expects a stable, homogeneous, and fine-pored foam. For brewers, there exists only limited possibilities that allow them to enhance the beer foam stability. The German Purity Law allows, for example, the option of increasing the hop dosage and thereby improving the beer foam. However, this also has an effect on bitterness and impacts the final sensory profile of the beer. The brewer may also choose different hop products; however there are no conclusive studies illustrating how conventional hop products (pellets type 90, ethanol extract, and CO2 extract) affect the foam stability of beer. Brewers who do not brew according to the German Purity Law may use foam enhancing products such as propylene glycol alginate, iso extract, and tetrahydro-iso extract. The positive influence of these products on foam stability has previously been published. With a growing trend toward natural products, the consumer increasingly looks favorably on natural ingredients. Therefore we used natural foam enhancers such as an α-acid extract and a yeast product for our research. Like other studies we used three foam analysis methods and a method to quantitatively calculate the percentage of foam cling adherence. In contrast to other studies, which evaluated foam stability, but neglected the sensory part, we did a sensory evaluation of the produced beers. All experimental beers were evaluated according to the DLG approved scheme. The bitterness of the hoppy beers produced was characterized in more detail by assessing them according to the Kaltner scheme. Additionally, reference photos of different beer foams were used to visually assess the foam of the brewed experimental beers. Our results showed that hop products, even conventional hop products, and other foam enhancers have different impacts on foam stability. Additionally we created a foam value (which included all foam methods) because foam analysis reacted differently to the used product. This means there is an increase in one foam measurement, but if measured with another stability test this increment is not detected. The sensory assessment revealed that some products had a negative effect on the sensory profile of the beer. In addition the foam texture of some products was very unnatural. It must also be mentioned that some hop products were difficult to handle.
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, finishing in 2006 as the best of the examination. Until beginning his studies, he worked as a brewer at the Bitburger brewery. In 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 and completed his diploma thesis on hop proteins. Since 2012 he has been working as a Ph.D. fellow at the Institute for Brewing and Beverage Technology in Weihenstephan. His research focus is the influence of texture and molecular composition of the foam on the flavor release from beer.