Hydroxyl radical oxidation of feruloylated arabinoxylan

• Arabinoxylan was isolated from wheat aleurone-rich flour (purity: 92% m/m d.m.).
• The arabinoxylan isolate formed gel upon peroxidase/H2O2 treatment.
• Hydroxyl radical oxidation did not induce oxidative gelation of arabinoxylan.
• Hydroxyl radical oxidation did not cause ferulic acid dimerization.
• Hydroxyl radical oxidation provoked viscosity decrease in AX solution.

Feruloylated arabinoxylan (AX) has a unique capacity to form covalent gels in the presence of certain oxidizing agents. The present study demonstrates that hydroxyl radical oxidation does not provoke ferulic acid dimerization and thus oxidative gelation. We studied the hydroxyl radical mediated oxidation of an alkali-extracted AX preparation (purity: 92 g/100 g dry matter) that showed gel-forming capability upon peroxidase/hydrogen peroxide treatment. Hydroxyl radicals were produced with ascorbate-driven Fenton reaction and the radical formation was monitored with electron paramagnetic resonance, using a POBN/EtOH spin trapping system. Oxidation was carried out at different catalytic concentrations of iron (50 and 100 μM) and at different temperatures (20 °C, 50 °C, and 80 °C). It was demonstrated that hydroxyl radical oxidation does not provoke gel formation, but viscosity decrease in AX solution, which suggests polymer degradation. Furthermore, it was demonstrated that hydroxyl radical formation in AX solution can be initiated merely by increasing temperature.