Analytical determination of antioxidant capacity of hop-derived compounds in beer using specific rapid assays (ORAC, FRAP) and ESR-spectroscopy

Abstract There is a relationship between antioxidant activity and ageing stability of beer. The high-throughput capacity assays ORAC FRAP, which rely on specific reaction mechanisms, are validated as an addition to the established ESR-ST method with focus hop-derived antioxidants. Beers were brewed systematic variations in hop variety, product, hopping regime (late hopping) achieve sample beers varying widely concentrations antioxidants (α- iso-α-acids, phenolic compounds). A significant positive correlation compounds ORAC- FRAP-values ( p < 0.01) was found. effect individual resinous substances free acids flavonoids beer (ORAC, ESR-ST) proven spiking trials. We found occurrence o-di-OH-group compounds. Phenolic did not react anti- or prooxidants radical generation (ESR-ST). Higher unisomerized α-acids significantly reduced ESR-signal intensity but had no FRAP-values. late addition, yielded higher compounds, ORAC, intensity. These three methods different principles, therefore, groups act these assays. combination two FRAP) advantageous for evaluation