Electron Paramagnetic Resonance-Driven Detection of Lipid-Derived Radicals in Bulk Oil and Emulsions: A Real-Time Analytical Strategy

Capturing transient free radicals during lipid transformation is critical for elucidating the underlying reaction mechanisms. Conventional methods rely on analyzing stable end products and often require time-consuming separation from complex heterogeneous systems. Electron paramagnetic resonance (EPR) spectroscopy offers unique advantages by enabling in situ detection of free radicals. This review surveys EPR applications in lipid oxidation studies across various oils and emulsions, focusing on four techniques: direct detection, spin trapping, spin scavenging, and spin labeling. Their reliability in predicting shelf life, elucidating oxidation mechanisms, assessing antioxidant capacity, and probing interfacial properties is evaluated. Factors that limit data interpretation accuracy and their mechanistic origins are indicated. The utility of EPR as a qualitative, semiquantitative, or quantitative tool is critically assessed. Finally, we provide practical guidance for selecting appropriate EPR methods and highlight how emerging technologies such as rapid-scan and high-field EPR can overcome current limitations and enable deeper exploration of interface-driven oxidation mechanisms.