Simple and Rapid Detection of Thermal Degradation Products of Cooking Oils Using a Benchtop MALDI-TOF Mass Spectrometer

Significance of the Topic

Monitoring thermal degradation in cooking oils is essential for food quality control and safety assessment. Degradation products formed during frying can affect flavor, nutritional value, and pose health risks. Rapid profiling of these compounds supports both research and industrial quality assurance.

Objectives and Study Overview

The study demonstrates a straightforward workflow for detecting heat-induced degradation products in olive oil using a compact benchtop MALDI-TOF mass spectrometer. It aims to illustrate how minimal sample preparation and rapid analysis can reveal molecular changes in heated versus unheated oils.

Methodology and Instrumentation

Samples of commercial olive oil were either unheated or heated at 180 °C for eight hours. Each sample was diluted in a hexane/diethyl ether mixture, mixed with a matrix solution of 2,5-dihydroxybenzoic acid in methanol and a sodium iodide cationization agent, then spotted onto a reusable MALDI target.
Fractionation was performed on silica gel 60, eluting nonpolar compounds with 90 % hexane/10 % diethyl ether and polar compounds with pure diethyl ether.
Analysis was carried out on the MALDI-8020 benchtop MALDI-TOF mass spectrometer in linear positive-ion mode, featuring a 200 Hz solid-state laser and a load-lock chamber for rapid target exchange.

Main Results and Discussion

Mass spectra of unfractionated oils showed sodium adduct peaks around m/z 881–907 corresponding to triacylglycerols (TAGs). Heated samples displayed additional peaks at m/z 923 and 939, indicating oxidized TAG species.
Analysis of the polar fraction revealed multiple β-scission fragments (m/z 783, 797, 823) and oxidized TAG dimers near m/z 1800. Structural assignments were made based on literature data, highlighting the diversity of degradation pathways including oxidation, fragmentation, and dimerization.

Benefits and Practical Applications

• Enables rapid molecular profiling of lipid oxidation without extensive chromatography.
• Requires minimal sample preparation, suitable for high-throughput screening.
• Applicable to quality control in food industries and research laboratories.
• Potentially transferable to analyses of proteins, glycans, and synthetic compounds.

Future Trends and Possibilities

• Integration of automated fractionation and data processing for routine monitoring.
• Extension to real-time analysis of frying oils and other food matrices.
• Development of reference libraries for rapid identification of degradation markers.
• Combination with tandem MS or imaging techniques for spatially resolved studies.

Conclusion

The benchtop MALDI-8020 MS offers a compact and efficient platform for detecting thermal degradation products in cooking oils. Its linear mode performance and simple workflow deliver rapid insights into molecular changes, with broad applicability across food quality, biological research, and industrial analytics.

References

• Ohtani H, Yamahashi Y, Ishida Y. Curing Behavior Analysis of Drying Oil using MALDI-MS. 58th Annual Conference on Mass Spectrometry, Japan, 2010.
• Picariello G, Paduano A, Sacchi R, Addeo F. MALDI-TOF MS profiling of polar and nonpolar fractions in heated vegetable oils. J Agric Food Chem. 2009;57(12):5391–5400.