Kinetic behaviour of radicals in packaged beer
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The understanding of beer oxidation is a longstanding research priority of brewers in order to extend beer shelf life. This paper reports on the oxidation of beer over 20 days while stored at 2, 21 and 30oC and over 437 days at 30oC. Two assays were employed to measure the oxidative stability: a lag time or EA (Endogenous Anti-oxidant activity) determination by use of EPR (Electron Paramagnetic Resonance) and a luminol-based hydrogen peroxide assay. An improved lag time determination from the EPR peak height data using a non-linear regression technique (piecewise regression) was developed. In both the 20-day trial and the extended trial at 30oC, the EA value or the antioxidant level remaining in the beer was found to decline and could be modelled by an apparent first order kinetics at all three temperatures. The effect of temperature on the EA value could be modelled by use of Arrhenius theory. The luminol-based hydrogen peroxide assay results indicated that the chemiluminescence or hydrogen peroxide concentration increased with storage time at 21 and 30oC.
Cerevisia: Belgian Journal of Brewing and Biotechnology