Scope and Limitations of Enzymatic Deoxygenating Methods to Improve Flavor Stability of Beer. C. Blockmans, M. Heilporn, and C. A. Masschelein, Institut des Industries de Fermentation, C.E.R.I.A., 1070 Brussels, Belgium. J. Am. Soc. Brew. Chem. 45:0085, 1987.

Flavor stability is increasingly becoming the limiting factor in shelf life of beer. Because deterioration of beer quality is closely related to oxidative changes-molecular or radical forms of oxygen are the major sources of aging flavor problems-complete elimination of the prime determinant, oxygen, would be expected to prevent off-flavors from developing during storage of packaged beer. To test this hypothesis, we used glucose oxidase-catalase to remove the oxygen from bottled beer. Surprisingly, although the enzyme system effectively removed oxygen, flavor was not efficiently stabilized. We demonstrate that the lack of correlation results from a rapid build-up of hydrogen peroxide, which is utilized by catalase for the coupled oxidation of ethanol and other oxidizable substrates in beer. A combined treatment with glucose oxidase and free sulfite largely prevented the peroxidative phase and almost completely suppressed oxidative reactions involved in flavor deterioration.

Keywords: Catalase, Coupled oxidation, Gluconic acid, Hydrogen peroxidase, Peroxidase, Stale aldehydes