iMProVeMent oF tHe oXidatiVe stabilitY oF beer

INTRODUCTION The overall purpose of the research project is to make it possible for breweries not using ‘active yeast’ in the bottles to produce beer that is oxidative stable for up to one year without the addition of sulfite or ascorbic acid. This is to be achieved by increasing our knowledge about how especially thiol-containing proteins affect the oxidative stability of beer and how the yeast during fermentation affect the content of reducing (antioxidative) components in the final beer. This knowledge will be communicated to Danish microbreweries through the Society for Danish Breweries (Danske Bryghuse) and DHI and will make it possible for the microbreweries by suitable selection of composition of malt, yeast strain, and fermentation conditions to predict and improve the stability of the final beer. The stability of bottled beer is very often limited by oxidative processes. Heat, light, and oxygen are all factors that promote oxidation and which hereby limits the stability of beer1. Sulfite, which is produced by the yeast during fermentation, has decisive influence on the stability of pilsner2. Sulfite works as an antioxidant, and it has been shown that when sulfite in beer is depleted, the resistance towards oxidative reactions disappear. In Denmark, it is permitted to improve the stability of beer by adding sulfite M a r i a n n e n . l u n d 1, n i l s a r n e b o r g 1, W i l l i a M F r a n k 2 & M o g e n s l . a n d e r s e n 1* . iMProVeMent oF tHe oXidatiVe stabilitY oF beer