P-59. Gallotannins—A useful tool to improve colloidal and oxidative beer stability

Presenter: Christof Reinhardt, Technische Universität Berlin, Institute of Food Technology and Food Chemistry, Chair of Brewing Science, Berlin, Germany
Coauthors: Thomas Kunz and Frank-Jürgen Methner, Technische Universität Berlin, Institute of Food Technology and Food Chemistry, Chair of Brewing Science, Berlin, Germany

In a highly competitive market place quality and consistency of beer have become of paramount importance. Besides beer flavor, color, and foam stability, one major attribute of beer quality is colloidal stability. If it comes to an undesirable haze during beer storage, the product is classified by the consumer as inedible. Although a variety of substances can be responsible for colloidal instability and haze formation, the most frequent and important form of non-biological haze formation has been identified as the interaction of proteins and polyphenols naturally occurring in beer. Our previous investigations have shown that metallic ions like iron with specific oxidation steps also have an important influence on the colloidal stability of beer caused by their influence on complex formation with protein-polyphenol compounds and oxidative stability. In order to obtain high colloidal product stability for a long period, it is necessary to remove the haze-active proteins and/or polyphenols using technological measures during the brewing process. Polyphenols are normally removed by nylon 66 or PVPP, while proteins can be removed with the help of silica gel or bentonite. In this correlation in the brewing industry it is increasingly popular to use gallotannins, as a high molecular weight tannic acid, to improve colloidal stability. When they are used in the process before filtration, they react primarily with haze-active acid SH-group containing proteins by adsorption and precipitation. The protein complexes that are formed are removed completely by filtration and are responsible for an increase in colloidal stability. Complexes that involve metallic ions like iron are also removed in this way. Consequently, a deceleration of oxygen activation and radical generation by the Fenton-Haber-Weiss reaction system is observable, resulting in a further advantage for colloidal and flavor stability as confirmed using EPR (EAP and T values), GC-MS (aging comp.), and other analytical methods. Our studies have shown that for the appropriate procedure (quantity, dosing point) the application of gallotannins is a good tool to increase oxidative and colloidal beer stability, resulting in lower formation of haze and typical aging compounds during storage.

After apprenticing as a brewer and maltster at the Braugold Brauerei Riebeck GmbH & Co. KG Erfurt (2004–2007), Christof Reinhardt started his studies at the Technische Universität Berlin in biotechnology with a concentration in brewing technology (2008–2013). He began his research in January 2011 as a student research assistant at the Technische Universität Berlin, Institute of Food Technology and Food Chemistry, Chair of Brewing Science. He is working on determining the impact of fermentable and nonfermentable carbohydrates and gallotannins on the flavor and oxidative and colloidal stability of finished beer using EPR spectrometry.

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