Oxidative treatments of solid olive residues: Effects on phenolic and fatty acid fractions

In the present study, we considered the effects of several chemical treatments of three different olive residues (pomace) of diverse origins, which all involve H2O2. Diluted (40 vol) and concentrated (130 vol; 30% wt) H2O2 was used alone or in combination with Fe sulfate (the Fenton system). The main goal was to oxidize the phenolic substances, as only a dephenolyzed sample can be safely used for applications like soil improvement or as biomass for biogas generation. The o‐diphenols were always oxidized in higher amount than single phenols as demonstrated by data on tyrosol and hydroxytyrosol. The Fenton system appears to be a method that can oxidize the phenolic fraction, while leaving only a trace of residual H2O2 inside the pomace. We also considered the effects of these oxidative treatments on the triglycerides. Linoleic acid was largely oxidized, although only in pomace with a low water content and in the presence of the Fenton treatment. Finally, the whole lignocellulose matrix of all of the pomaces was recovered at the end of treatment without any large changes, as shown by the IR spectra of oxidized samples.