Tobias Teumer (1), Frank-Jürgen Methner (2), Matthias Rädle (1); (1) University of Applied Science, Mannheim, Germany; (2) Technische Universität Berlin, Berlin, Germany


In some steps of food engineering processes, particularly after brewed beer gets filtered, unwanted reactions can take place in the solution, such as coagulation or the appearance of other disperse phase products. However, the filtered beer should be free of particles. After filtration, beer haze can form through oxidation caused by insufficient stabilization steps. Known coagulation processes are either pure protein complexes or protein–phenol complexes, as well as oxalate precipitation that results from other processes. To get a better understanding of this formation process it is possible to make in-line measurements of the refractive index of the disperse-phase, the particle size, and concentration with high time resolution. Gluten is used in a solution together with ethanol to analyze the protein precipitation that consists in equal proportions of the amino acids glutelin and prolamin. Both amino acids precipitate at a pH value between 4.2 und 5.2 at the isoelectric point. In a second comparison study, oxalate precipitation gets analyzed. First, a fast optical measuring technique with 2,300 measurements/second/channel is used with two different wavelengths, 450 nm and 650 nm, to observe particle growth. Second, a slow measuring technique is developed with roughly 5 measurements/second to acquire a full spectra in the visible range to determine particle growth. Supported by mie theory calculations the necessary material values get adjusted. Concentration and pH value interference with the particle growth are shown and validated through light microscopy reference measurements. With this forthcoming knowledge toward precipitation reactions in beer, improved quality measurement equipment for the brewery industry can be developed.

Tobias Teumer received a Dipl.Ing. (FH) in process engineering in 2009 and a M.S. degree in chemical engineering in 2011 at the University of Applied Sciences in Mannheim. He is employed at the Institute of Process Control and Innovative Energy Conversion, where he is working in the area of spectroscopy and back scattering. He currently is writing his Ph.D. thesis on beer haze at the Technical University of Berlin.