Effect of Model Lignin Structures on the Oxidation of Unsaturated Fatty Acids

Abstract

The aim of this study is to better understand vegetable oils as raw materials in the application of wood protection in order to obtain improved durability of exterior wood materials in an environmentally friendly way. This was done by studying the effect of lignin model compounds on the auto-oxidation rate of methyl linoleate. The auto-oxidation process of methyl linoleate was measured by itself and in combination with 1 wt% phenolic and non-phenolic lignin model compounds at 70°C. The effect of lignin compounds on the methyl linoleate auto-oxidation process was monitored by ¹H-NMR, size exclusion chromatography (SEC), and real-time infrared spectroscopy (RT-IR). It was observed that phenolic groups and radical conjugation are the main contributors to an antioxidant effect of lignin compounds on the oxidation rate of the methyl linoleate. Ferulic acid, which is phenolic and contains a carboxylic group, has the largest antioxidant effect on methyl linoleate. It was also found that the antioxidant effect existed, despite the low solubility of ferulic acid in methyl linoleate. This research demonstrates that it is possible to follow the auto-oxidation process in real time to uncover the effects of wood constituents on the fatty acid auto-oxidation process. Additionally, this knowledge that drying rate of oil can be tuned with the addition of lignin compounds can be used to predict drying times when this oil is applied to different species of wood.

Keywords

Drying oils Oxidative drying Methyl linoleate Wood protection Model lignin compounds

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