Dual-Method Approach for Edible Oil Oxidation Analysis: LC-MS/MS and Near-Infrared Spectroscopy

Edible oils are prone to oxidation when exposed to heat, light, or other environmental factors, leading to quality deterioration. To preserve the quality of edible oils, it is crucial to assess not only the extent of oxidation but also its oxidation mechanisms. Depending on the oxidation mechanisms, triglycerides (TG), the primary components of edible oils, are oxidized into various TG hydroperoxide (TGOOH) positional isomers. Although these isomers exhibit similar structures, we have successfully identified TGOOH isomers using liquid chromatography coupled with mass spectrometry (LC-MS/MS). Since then, this method clearly has determined the mechanisms that contribute to edible oil oxidation. Recently, to facilitate the analysis of edible oil oxidation mechanisms, we developed a more convenient analytical method using near-infrared (NIR) spectroscopy, based on our established LC-MS/MS approach. In this presentation, I will introduce and discuss both the LC-MS/MS and NIR methods as described below.
     LC-MS/MS analysis revealed increased TGOOH isomers specific to photo-oxidized and thermally oxidized canola oil. Principal component analysis (PCA) of NIR spectra identified wavelength regions capable of distinguishing thermal oxidation from photo-oxidation. Partial least squares (PLS) regression analysis, using TGOOH concentration as the objective variable and NIR spectra as the explanatory variable, produced a robust calibration model (coefficient of determination: 0.994-0.998 ; ratio of performance to deviation: 7.25–8.24) for each TGOOH isomer. Hence, this study successfully established a method to identify canola oil oxidation mechanisms using FT-NIR spectroscopy and to quantify TGOOH isomers. Loading plots analysis revealed that these models were created because NIR spectra capture trace changes of the peak around 6980 cm^-1(-CH₂-) and 5260 cm^-1 (H₂O) derived by different oxidation mechanisms (i.e. radical and/or photo-oxidation). The application of this method to various edible oils is expected to enable simple and rapid quality evaluation.