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P-51. Brewing with fermentable and non-fermentable carbohydrates addition—Impact on oxidative reactions and formation of specific aging compounds

Presenter: Niklas O. Brandt, 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

Carbohydrates are very important in human nutrition since they are used in the food and beverage industries. In this study the influence of fermentable and commonly used non-fermentable sugars on oxidative processes and the formation of specific aging compounds during beer production were evaluated. In previous investigations, the reducing potentials against Fe3+ of different sugars at low pH were determined using an optimized Chapon method. These results were in conflict with widely accepted general classifications of sugars into reducing and non-reducing species. The properties of carbohydrates at alkaline pH are well known, but in pH areas of wort and beer the properties of carbohydrates change depending on the type of sugar. For example, the so-called reducing sugar glucose loses its reducing potential, whereby the reducing capacity of sucrose rises because of an acidic hydrolysis splitting and the strong reducing capacity of the generated fructose at low pH ranges. The aim of these investigations was to gain better insight into the influences of different carbohydrates during brewing, with a focus on oxidative wort and beer stability. Thereby, the influence of sugar additions on aging compounds (oxygen indicator: 3-/2-methylbutanal) were evaluated in wort and beer by GC-MS and compared to the antioxidative potential measured via EPR spectroscopy (EAP and T values), as well as reducing potentials against Fe3+ (optimized Chapon method) and SO2 contents. In correlation with the measured reduction potential, the sugars show the opposite effect on oxidative processes during wort boiling by the formation of specific intermediate Maillard reaction products with a reductone/endiol structure. An acceleration of radical generation by the Fenton-Haber-Weiss reaction mechanism and the formation of specific aging compounds follows. On the other side, sugars raise the osmotic pressure on yeast during fermentation, leading to higher sulfur dioxide production, which could act as an antioxidant by scavenging ROS and binding aldehydes in carbonyl complexes. The results show that sugars influence the pro- and antioxidative system of beer directly and lead to the suggestion for improvement of beer’s shelf life by adding non-fermentable sugars just before fermentation, so the negative effect on radical generation during wort boiling can be avoided and the positive influence on SO2 formation during fermentation is utilized.

Niklas Brandt started his brewing career with an internship in a craft brewery in Lower Saxony, Germany. Afterward, he began an apprenticeship as a brewer and maltster at the Brauerei Beck & Co. in Bremen (AB InBev Germany), which he successfully completed (2007–2009). Since October 2009 Niklas has been studying brewing and beverage technology at the Technische Universität Berlin. His bachelor degree study was finished in April 2013, and he is currently working on his master’s degree studies. In addition to these studies, Niklas began research work in January 2011 as a student assistant at the Technische Universität Berlin, Institute of Food Technology and Food Chemistry, Chair of Brewing Science. It was here that his bachelor degree thesis work, dealing with research on sugars during brewing, was done. Niklas also works on the EPR spectrometer and assists with different projects in the laboratory and pilot brewery.

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