Accumulation of Hydrogen Peroxide in Barley Seeds – A Key Factor for Malt Quality?

Abstract

Hydrogen peroxide (H2O2) is a reactive oxygen species that contributes to undesired oxidation of barley ingredients that are crucial for beer production and quality. H2O2 reveals a dual role in plant physiology as it is involved in oxidative damage of biomolecules, but also actively synthesized for growth regulating processes. As H2O2 formation in barley and its consequences for malt quality have not been investigated before, a method for H2O2 quantification throughout malting is presented in this work to investigate this pathway's potential involvement in oxidative reactions in malt production. During germination, H2O2 steadily accumulated in the barley seeds reaching concentrations up to approximately 2.5 µmol/g (dm). Barley variety, aeration rate, as well as water content during steeping were significant impact factors for H2O2 formation. H2O2 strongly correlated with the barley acrospire lengths indicating its beneficial involvement in growth regulation. During withering and kilning, the majority of H2O2 was exponentially degraded. It is proposed that after its controlled synthesis during germination, H2O2 acts as a primary oxidant of malt ingredients during withering and kilning. The barley metabolism-derived H2O2 accumulation is discussed in relation to oxidative stability of malt, wort, and beer. The data of this work can be used as a fundament to control oxidative damage during malting.