Finishing and Stability Session
Petr Kosin, Budejovicky Budvar, n.p., Ceske Budejovice, Czech Republic
Co-author(s): Jan Savel and Adam Broz, Budejovicky Budvar, n.p., Ceske Budejovice, Czech Republic
ABSTRACT: Beer stability is usually determined by forcing
tests based on acceleration of beer aging. The bottles or cans
containing beer are placed in heating or cooling bathes, and aging of
beer is estimated. Aging is a typical process connected with undesirable
changes in beer. They comprise increasing color, haze formation, and/or
sensory changes. More procedures are used to accelerate beer aging such
as storage at higher temperature, oxidizing agent addition, or light
illumination. The substances, which can prevent such changes, are
usually called antioxidants, although they can also act as pro-oxidants.
Ascorbic acid and sulfur dioxide are examples of such substances. Beer
aging can be slowed down by other stabilizers such as PVPP, although
they are sometimes considered to have adverse effect, e.g., decrease of
polyphenol content. Samples with different amounts of stabilizers are
usually tested, but working with many packages is difficult and
time-consuming. Oxygen strongly supports beer aging, but its measurement
in a package is difficult and inaccurate. Laboratory tests can
therefore hardly estimate the influence of oxygen on beer stability. We
usually need to prepare many samples with different amounts of tested
substances. Indirect measurements, such as reduction power or
antioxidant capacity determination, are often used in the presence of
air although the results strongly depend on the concentration of oxygen.
The solution is to prepare aerated or nitrogenated samples of beer with
air or nitrogen in the headspace in the range, which can occur in
practice. The ratio between liquid and gas volume in test vials
determines the total oxygen content, and their vertical or horizontal
position controls the rate of oxygen consumption. The entrance of air
after testing enables the beer to reach oxygen saturation again, which
is important for measurement of redox potential changes. After sample
heating and cooling, the differential spectra or haze are measured to
estimate the influence of the addition of various stabilizers. Dyes such
as methylene blue or indigocarmine are used as internal standards to
recognize the decrease in the reduction power of beer or degradation
power of oxygen radicals. 1,2-Diaminobezene is added to compare the
reactivity of sugar dicarbonyls to alpha-amino nitrogen. Another
strategy is to measure the concentration of traditional stabilizers such
as ascorbic acid or sulfite during heating of aerated or deaerated
beer. During aging the concentration of inhibitors decreases, so the
decay can be used for the measurement of their efficiency. Various
analytical methods can be used for this purpose.
Petr Kosin
received engineering (M.S. equivalent, 2006) and Ph.D. (2012) degrees in
brewing and malting at the Institute of Chemical Technology Prague,
Czech Republic. He worked on both of his theses, “Application of Modern
Methods for Yeast Activity Control in Brewery” and “Consumer Perception
of Beer Qualitative Characteristics,” at Budweiser Budvar, N.C. in Ceske
Budejovice. He has been working in research and development at
Budweiser Budvar, N.C. since his graduation. He has been a member of the
EBC Brewing Science Group since 2011.
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