Effect of Pasteurization on the Protein Composition and Oxidative Stability of Beer during Storage

The impacts of pasteurization of a lager beer on protein composition and the oxidative stability were studied during storage at 22 degrees C for 426 days in the dark. Pasteurization clearly improved the oxidative stability of beer determined by ESR spectroscopy, whereas it had a minor negative effect on the volatile profile by increasing volatile compounds :hat is generally associated with heat treatment and a loss of fruity ester aroma. A faster rate of radical formation in unpasteurized beer was consistent with a faster consumption of sulfite. Beer proteins in the unpasteurized beer were more degraded, most likely due to proteolytic enzyme activity of yeast remnants and more precipitation of proteins was also observed. The differences in soluble protein content and composition are suggested to result in differences in the contents of prooxidative metals as a consequence of the proteins ability to bind metals. This also contributes to the differences in oxidative stabilities of the beers.