NMR-enabled mapping and modelling of oxidation pathways in vegetable oils

Lipid oxidation is a major threat to the shelf-life of vegetable oils. Developing solutions to prevent oxidative spoiling currently requires empirical testing of shelf-life. The common approach of testing secondary oxidation markers in accelerated shelf-life testing is, however, time- and resource-consuming. Using primary lipid oxidation products as early markers has been shown to provide a rapid and cost-effective alternative. The scope of this approach is however limited to vegetable oils with specific fatty acid compositions and shelf-life conditions. Bottlenecks in widening the scope are lack of -1- methods that quantitatively cover primary and secondary oxidation products and -2- kinetic description of lipid oxidation pathways. In this work, we first implemented 1D and 2D qNMR methods at 600-950 MHz by which we quantitatively cover primary and secondary lipid oxidation products. ¹H and ¹³C NMR spectral assignments were made for the oxidation products for the dominant fatty acids in vegetable oils, i.e. oleic (O), linoleic (L) and linolenic (Ln) acids. The spectral assignments comprised lipid peroxides, epoxides, alcohols, ketones and aldehydes and thus covered the full map of lipid oxidation pathways occurring in vegetable oils. The spectral assignments and the use of 1D and 2D qNMR methods enabled quantification of temperature-dependent kinetics of oxidative pathways in OOO, LLL, LnLnLn triglyceride model vegetable oils at different temperatures. The assessment of the corresponding activation energies allowed for predicting lipid oxidation kinetics of vegetable oils with known (O, L, Ln) fatty acid compositions at a given temperature. These predictions were in excellent agreement with experimental determined lipid oxidation kinetics of vegetable oils.

References

1. Boerkamp, V. et al. Food Chemistry 390, 133145 (2023).
2. Nguyen, K.A. ; et al. Food Chemistry 433, 137266 (2023).

Acknowledgments: Netherlands Science Foundation (NWO), Dutch Ministry of Economic Affairs for financial support.