M-47: Influence of formation of hot trub and kinetic chemistry during wort boiling

Y. Huang (1), J. TIPPMANN (1), T. Becker (1); (1) The Chair of Brewing and Beverage Technology, Technical University Munich, Freising, Germany


During wort boiling, hot trub is formed, which contains about 55% proteins, 20% bitter substances, 20–30 other organic substances, and 3–5% minerals. The formation of hot trub is due to the denaturation and coagulation of nitrogen substances. The thiol (R-SH) and disulfur bridges (R-S-S-R) play an important role in making higher molecular weight proteins. The object of this study was to find out the important influencing factors involved in the formation of hot trub. Wort with three different gravities, concentrations of polyphenols, concentrations of alpha-acids, and concentrations of total nitrogen was boiled on a laboratory hotplate for 1 hr at three different boiling temperatures and three different rotation speeds. The concentration of coagulated nitrogen in wort, total nitrogen, and hot trub were measured. The face-centered design of the response surface methodology and statistical analysis resulted from the software used, Stat Ease Design Expert. The concentration of coagulated nitrogen was developed as a function of process parameters. Additionally, according to the function, the free energy of activation and the reaction rate constant (k) of the formation of hot trub were investigated. We developed a kinetic model to simulate the concentration of hot trub during the wort boiling.

Yarong Huang studied brewing science and beverage technology and graduated with a Dipl.-Ing. degree in brewing and beverage technology from the Technical University Munich (TUM) in 2009. Since 2009 she has been employed as a Ph.D. student in the field of brewing research, investigating the chemical reactions of important process markers during wort boiling processes at TUM in Freising-Weihenstephan, Chair of Brewing and Beverage Technology (Thomas Becker).

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