P-54. Beverage antioxidative index (BAX)—An innovative method for the evaluation and improvement of the beer flavor stability

Presenter: Victoria Schiwek, 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

For the prediction of beer flavor stability electron spin resonance (ESR) spectroscopy has been used for determination of lag time in the last decades. Previous investigations demonstrated that the lag-time measurement used up to now falsifies the results for oxidative flavor stability due to an increasing pH value during the analysis caused by the spin trap reagent (PBN). Against this background, a new EAP determination was developed that excludes falsifications and offers a new index number for the evaluation of flavor stability: the beverage antioxidative index (BAX). As a complement to EAP determination, BAX provides additional information about the interplay of anti- and pro-oxidative beer ingredients independent of SO2 content and about the consumption rate of the antioxidative potential during storage. In this study, BAX determination was used to demonstrate the influence of metal ions, pH, and Maillard reaction intermediates. Additionally, the correlation between BAX, beer color as an indicator of Maillard reaction products in the beer matrices, and formation of typical aging compounds during storage could be demonstrated. The investigations clearly demonstrate that lower pH values improve oxidative beer stability, as reflected by higher EAP, lower radical generation, and higher BAX values. Iron entry caused by raw materials and kieselguhr filtration deteriorate oxidative stability, and polyphenols do not change EAP and BAX significantly. Furthermore, it could be illustrated that hop ingredients like alpha- and beta-acids can act as a chelating agents and influence radical generation significantly and reduce oxidative processes. It could also be verified that specific intermediate Maillard reaction products with a reductone/endiol structure formed during kilning and wort boiling can decrease oxidative stability by the acceleration of the Fenton-Haber-Weiss reaction system and can have pro-oxidative properties. Corresponding to this, stronger generation of specific aging compounds (oxygen indicator) with higher color and lower BAX is detectable during beer aging. EAP determination facilitates a genuine examination of flavor stability. In combination with BAX determination, it is possible to get a deeper insight into the influences of different beer ingredients on flavor stability. An additional advantage of BAX is the indirect determination of SO2 content by linear regression.

Victoria Schiwek studied pharmaceutical and chemical engineering at the Beuth University of Applied Sciences from 2002 to 2007. The topic of her diploma thesis was “Optimized Analytical Methods for the Determination of SO2 in Beer and Malt.” After graduating, she worked as a chartered engineer in the field of instrumental analysis, particularly HPLC and IC, at VLB-Berlin (2007–2009). Since 2010 she has worked as vice head of laboratory for the Research Institute of Brewing Science, Technische Universität Berlin (Berlin Institute of Technology).

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