THOMAS KUNZ (1), Eon-Jeong Lee (1), Frank-Jürgen Methner (1)
(1) Berlin Institute of Technology (TU Berlin), Department of Biotechnology, Chair of Brewing Sciences, Berlin, Germany
Several breweries use unfermentable sugars to increase the beer
palate fullness. Besides the direct addition of sugars to the final
beer, it is a standard custom to add these sugars at the end of the wort
boiling process prior to fermentation; especially for low-solubility
sugars. The aim of this study was to investigate influences of the
addition before fermentation of commonly used unfermentable sugars
(polydextrose, palatinose, and trehalulose) in direct comparison to
fermentable sugars (glucose and sucrose) on the fermentation process,
palate fullness, beer flavor, and SO2 formation. The amount
of sugar (fermentable and unfermentable) added to basic wort (10.5%
original gravity) was calculated to achieve a realistic increase in
final extract of 1, 2, 3, and 5%. Control fermentation with no sugar
added (10.5%) and 12% extract was also performed. The fermentations were
carried out simultaneously and under the same conditions. Yeast growth,
SO2-production, extract, and pH development of every trial
was monitored. After fermentation and filtration, the beers were
analyzed (viscosity, extract, pH, color, SO2 content, etc.).
Additionally, a trained sensory panel tested every trial with special
focus on palate fullness, sweetness, and flavor in direct comparison to
the control beer where 0% sugar was added (pilsner type). In comparison
to the control fermentation, a higher SO2 formation was
generally observed in the brews where no sugar was added. Sugar
additions (fermentable and unfermentable) up to 1–2% yielded a
significant increase in SO2 content. Compared to unfermentable sugars, higher glucose and sucrose additions (>2%) resulted in higher SO2 contents of the finished beers. It seems that the general increase in SO2 is based on the osmotic pressure change in the wort. Besides this, the addition of fermentable sugars leads to a higher SO2
formation because of a stronger increase of the yeast cell number at
beginning of fermentation. At higher sugar concentrations (2–5%), the SO2
formation preponderates at the beginning of fermentation during the
exponential growth phase of the yeast. This correlation is confirmed by
the different influences of unfermentable sugars on the SO2
formation. With respect to the trials with unfermentable sugars, it
could be observed that the addition of polydextrose leads to a
diminished SO2 formation compared to palatinose and
trehalulose mainly due to the smaller influence of polydextrose on the
osmotic pressure of the wort. In summary, the results show that the
addition of unfermentable sugars to 2% leads to a better palate fullness
and higher concentration of antioxidant substances like SO2 without a detectable influence on the beer flavor or sweetness.
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 starting to study 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 Biophysics
at Saarland University (2002–2004). Since 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.
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