Presenter: Thomas Kunz, Berlin Institute of Technology, Department of Biotechnology, Chair of Brewing Sciences, Berlin, Germany. Coauthor(s): Eon-Jeong Lee, Christof Reinhardt, and Frank-Jürgen Methner, Berlin Institute of Technology, 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 the influence of the addition before fermentation of commonly used unfermentable sugars (polydextrose, Palatinose™ (isomaltulose) and Vitalose® (contains mainly trehalose) 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%. A control fermentation with no sugar addition (10.5%) and 12% extract was also performed. The fermentations were carried out simultaneously and under the same conditions. Yeast growth, SO2 formation, 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, higher SO2 formation was generally observed in the brews in which sugars were 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 in the yeast cell number at the beginning of fermentation. At higher sugar concentrations (2-5%), there is a preponderance of SO2 formation 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 SO2formation. With respect to the trials with unfermentable sugars, it could be observed that the addition of polydextrose leads to diminished SO2 formation compared to Palatinose™ (isomaltulose) and Vitalose® 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 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 EPR 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 EPR spectroscopy.