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.