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.

Keywords:

• Flavor stability
• hydrogen peroxide
• malting
• oxidative malt quality deterioration