J. P. MAXMINER (1), R. White (2), J. McMaster (3), D. J. Cook (1);
(1) University of Nottingham, School of Biosciences, Loughborough, U.K.;
(2) Molson Coors Ltd., Burton on Trent, U.K.; (3) University of
Nottingham, School of Chemistry, Nottingham, U.K.
Stability
Wednesday, June 4 - 3:00 p.m.-4:45 p.m.
Level 3, Crystal Room
As multinational brewers export their products to distant markets,
products are exposed to longer and more challenging storage conditions.
Beer, as manufactured, is not at chemical equilibrium and undergoes
complex chemical reactions during storage, which can lead to undesirable
changes in its sensory characteristics. This is a major challenge for
the brewing industry as it hinders the supply of a consistent product to
consumers. Since beer contains more than 600 volatile compounds, beer
flavor change is a complex field of research, and the dependable
prediction of shelf life remains a top research priority. Recently,
electron spin resonance (ESR) spectroscopy has received much attention
as a technique to predict flavor stability. It measures the resistance
of a beer sample to free radical-induced oxidative change. However,
there is a lack of consensus about the predictive power of ESR
measurements compared with other chemical assays or sensory analysis
techniques. This project involves the optimization and appraisal of an
ESR measurement protocol as a predictor of shelf life. Gallotannins are
known to act as metal-chelating agents and, thus, can disrupt the Fenton
reaction, which plays an important role in the formation of radical
oxygen species. Furthermore, there is evidence that gallotannins can act
as reducing agents and radical scavengers. In the present trials, the
effects of brewhouse addition of gallotannins on the flavor stability of
a lager-style beer were investigated. At pilot scale (16 hL),
gallotannin additions in the mash conversion vessel (3 g/hL of finished
beer) or wort kettle (2.5 g/hL of finished beer) were compared to
control brews. Effects of the additions were monitored at key points in
the production process and through to packaged beer. The second trial
was performed on a large-scale production line (1,500 hL) using the same
addition regimes as at pilot scale. Packaged beer was analyzed fresh
and after 3, 6, and 9 months of storage at 20°C. Analyses included the
measurement of antioxidant capacity via ESR spectroscopy; staling
aldehydes via solid-phase microextraction (SPME)-GC-MS with on fiber
derivatization; thiobarbituric acid index (TBI); metal ion content via
inductively coupled plasma mass spectrometry (ICP-MS); sulfur dioxide
via distillation; and sensory analysis. Results will be presented that
illustrate the effects of gallotannin additions on beer flavor
stability. Furthermore, different approaches to the analysis of ESR data
will be compared and the results evaluated against other chemical
staling indices as predictors of sensory shelf life. ESR measurements of
the pilot-scale wort samples directly before and after addition of
gallotannins showed a marked decrease in wort T160 values and
in the cooled wort TBI relative to control brews. However, these
improved wort parameters did not translate into improvements in ESR lag
times for finished beers at either scale of operation, reasons for which
will be discussed in light of the full sensory and analytical results
for each trial.
After receiving a Dipl.-Ing. (FH) degree in beverage technology from
the University of Applied Science Wiesbaden-Geisenheim (Germany), Jörg
Maxminer worked at the Karlsberg Brewery in Homburg (Germany) in the
Technology and Development Department for two years. In 2011 he
graduated from Heriot-Watt University Edinburgh (U.K.) with an M.Sc.
degree in brewing and distilling. Jörg is currently working toward a
Ph.D. degree at the University of Nottingham (U.K.), with a research
focus on flavor stability of lager-style beers. Aside from work, Jörg
enjoys helping out at the family-owned winery and distillery back in
Germany, brewing his own beer, and playing handball.
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