Iso-α-acids, bitterness and loss of beer quality during storage

The attractive flavor of beer changes rapidly upon storage and limits the shelf life of this beverage. This degradation is due to several factors that may be associated with the vulnerability of iso-α-acids to light and the oxidation of iso-α-acids. These compounds are responsible for the beer bitterness and its characteristic flavor. Apart from adequate beer packaging, there are several methods which can minimize the degradation of iso-α-acids: addition of phenolic compounds with antioxidant properties, addition of pure stereoisomers cis-iso-α-acids or their reduced species, or use of riboflavin-binding proteins.

► Iso-α-acids derive from the thermal isomerization of α-acids during brewing process.
► The changes during beer storage are associated with the vulnerability of iso-α-acids.
► Addition of antioxidants, iso-α-acids, or reduced iso-α-acids provides beer stability.