36 - The Chemistry of Aging Beer

Abstract

Packaged beer is a closed system that continuously will be submitted to alterations by chemical reactions. These alterations will lead to perceivable changes in flavor, foam and colloidal stabilities. In this chapter, the underlying mechanisms of the reactions leading to aging of beer are discussed. Radical reactions, often initiated by reactive oxygen species, have an important contribution to beer staling and form a continuous thread to the stability of beer. Oxidation of unsaturated fatty acids and Maillard reactions leads to hundreds of different compounds. Furthermore degradation of hop bitter acids and carotenoids, oxidation of polyphenols, hydrolysis of glycosides and esters or synthesis of esters, acetalization of aldehydes will all contribute to the aging of beer. When using antioxidants, attention has to be paid to the slower reacting oxygen species such as H2O2, rather than the most reactive species as the hydroxyl radical.