Technical Session 08: Sensory Session
Thomas Kunz, Technische Universität Berlin, Department of Biotechnology, Chair of Brewing Sciences, Berlin, Germany
Co-author(s): Torsten Seewald, Niklas Brandt, Christof Reinhardt, and
Frank-Jürgen Methner, Technische Universität Berlin, Department of
Biotechnology, Chair of Brewing Sciences, Berlin, Germany
ABSTRACT: The aim of this study was to investigate the
influences of fermentable and commonly used unfermentable sugars,
usually added during wort boiling to increase the beer’s palate
fullness, on oxidative processes during wort boiling, the SO2
formation, palate fullness, flavor, and formation of specific aging
compounds. The first results demonstrate that the increase of osmotic
pressure by addition of non-fermentable sugars is responsible for higher
SO2 formation during fermentation. Addition up to 2% prior
to fermentation leads to a better palate fullness and higher
concentration of antioxidant substances like SO2 without
notable influence on flavor or sweetness directly after filling.
Otherwise, a previous investigation showed that sugars behave
differently at low pH than the generally known behavior described by
Fehling, resulting in a sugar type specific influence on oxidative
processes during brewing and beer storage. The newly developed “Chapon”
method (MBAA 2011) demonstrates that at low pH (4.2), the strongest
reducing potential results from isomaltulose followed by fructose,
Vitalose®, and maltotriose. The low reduction potential of the so called
“reducing sugar” glucose at low pH can be explained by the inhibited
formation of the open-chain aldehyde structure. In contrast, fructose
possesses a higher ability to generate the open-chain-structure,
resulting in stronger reducing properties. In this context the
increasing reducing potential of the “non-reducing sugar” sucrose
results from the acid hydrolyzed formation of invert sugar. Additional
investigations at higher temperatures (90°C) and pH (5.2) provide
evidence about the behavior of fermentable and unfermentable sugars
during wort boiling. As a result the strong reducing potential of
maltotriose in comparison to maltose is remarkable. In addition, the
partial unexpected reduction potentials of sugars in the pH range of
wort and beer have a direct influence on oxidative processes. In
correlation to the measured reduction potential, the sugars show the
same effect on oxidative processes during wort boiling as specific
intermediate Maillard reaction products with reductone/endiol structure,
resulting in an acceleration of radical generation (EPR spectroscopy)
by the Fenton-/Haber-Weiss reaction mechanism and the formation of
specific aging compounds (GC-MS oxygen indicator: 3-/2-methylbutanal).
This phenomenon is demonstrably caused by the rapid reduction of Fe3+ to Fe2+
in direct dependence with the reduction properties, resulting in a
higher activation of oxygen and stronger radical generation. In
consideration of the reduction properties, the sugar profile of the wort
should be characterized by a low content of fructose and maltotriose.
In the case of non-fermentable sugars addition during wort boiling is
disadvantageous. Our recommendation is direct addition before
fermentation to avoid the negative effects on radical generation and to
use the positive effect on SO2 formation during fermentation.
Additional experiments provide information on the influences of the
types of unfermentable sugar used on oxidative processes, aging
compounds, and taste during storage.
After qualifying as a
certified technician in preservation engineering (1991–1993), Thomas
Kunz completed his basic studies in chemistry at the University of
Applied Sciences, Isny (1994–1995), and his basic studies in food
chemistry at Wuppertal University (1995–1998), before studying food
technology at the University of Applied Sciences, Trier (1998–2002).
After graduating, he worked as a chartered engineer in the area of ESR
spectroscopy at the Institute of Bio Physics at Saarland University
(2002–2004). Since January 2005, he has been employed as a Ph.D. student
at the Research Institute of Brewing Sciences, Berlin Institute of
Technology (Technische Universität Berlin). His main research focus lies
in analyzing radical reaction mechanisms in beer and other beverages
using ESR spectroscopy.
VIEW PRESENTATION 27
