Relationship of iso-α-acid content and endogenous antioxidative potential during storage of lager beer

Abstract

One of the critical issues regarding the quality of beer is the change in its chemical composition that occurs during storage. Decomposition of iso-α-acids results in an undesirable decrease in bitterness as well as a deterioration in the sensory profile of the beer. These changes are caused by the susceptibility of iso-α-acids to degradation owing to the influence of reactive oxygen species and light. The aim of this study was to investigate the influence of storage conditions (temperature, light) on the degradation of iso-α-acids during aging, with the main focus on monitoring the relationship between the turnover of iso-α-acids, the sulphur dioxide content and the antioxidative potential of stored beer as measured by electron spin resonance spectroscopy. In agreement with previous investigations, a significant decrease in the content of bitter compounds (up to 18 % relative to the original level, depending on storage conditions) was observed. A significant decrease in the antioxidant potential of beer was recorded simultaneously and the data confirmed a strong correlation between these parameters. The decline in beer bitterness could become a marker for estimating oxidative damage during storage.

Technological influence on sensory stability and antioxidant activity of beers measured by ORAC and FRAP

“…We found no significant differences in overall bitterness quality (DLG score) or bitter aging score for force‐aged and naturally aged samples brewed from different malts. Apart from the sensory description of bitterness, we measured the decline in bitter iso‐alpha‐acids in the naturally aged beers (Table ) as an analytical marker for oxidative beer aging . No significant differences between the hopping regimes were found for the absolute decline in iso‐ α ‐acids.…”

“…In a study by Karabín et al . (2014), decline in iso‐ α ‐acids correlated with the decline in antioxidant potential during beer storage . The degradation of iso‐ α ‐acids was therefore used in this study as a marker for oxidative beer aging apart from changes in sensory attributes.…”

“…Staling aldehydes arise from the oxidation of fatty acids, the Strecker degradation of amino acids, the release of bound aldehydes during beer storage, the Maillard reaction, melanoidin catalyzed oxidation of higher alcohols, and the degradation of bitter acids . The degradation of bitter iso‐ α ‐acids was described as an important analytical marker for oxidative beer aging by a number of authors . Oxidative degradation reactions play a central role in the loss of bitter acids during beer storage .…”

Possibilities to improve the antioxidative capacity of beer by optimized hopping regimes

“…However, newer studies (26) using a 2-deoxyribose oxidative degradation assay revealed that both hop αand iso-α-acids are capable of suppressing radical formation by complexing iron, but are incapable of scavenging hydroxyl radicals. Other authors (52)(53)(54) have claimed that the oxidative degradation of iso-α-acids in beer plays a role in beer staling, but to a minor degree.…”

Sulfites in beer: reviewing regulation, analysis and role

“…Additionally, the concept of Endogenous Antioxidant (EA) value, which is the time taken before an ESR signal is developed in an aging test, showed a clear relationship between the EA value and sulfite level in beer (Uchida and Ono, 2000). More recently, Karabín and co-authors have shown that one of the reasons for the decline in the endogenous antioxidative potential of beer during storage is a significant decrease in SO 2 content, probably caused by chain oxidation reactions catalysed by transition metal ions, particularly ferric ions (Karabin et al, 2014).…”