Thermal Oxidation of Cyclopropene Fatty Acids: Kinetics and Reaction Mechanism Based on Degradation Products

Cyclopropene fatty acids (CPE‐FAs), predominantly consisting of sterculic acid and malvalic acid, are a class of naturally occurring fatty acids featuring a cyclopropene moiety. They have been proven to induce physiological disorders in various animal species. In this study, kapok seed oil—characterized by high CPE‐FAs content and ready accessibility—was selected as substrate to systematically investigate the regularities and kinetic characteristics of CPE‐FAs thermal oxidative degradation during heat treatment at 150°C–250°C. The results showed that the conversion of CPE‐FAs exhibited a strong dependence on temperature. A particularly sharp increase in the degradation rate of malvalic acid was observed at 210°C, where 91.8% degradation was achieved in merely 30 min of heating. Furthermore, headspace solid‐phase microextraction coupled with gas chromatography–tandem mass spectrometry (HS–SPME–GC–MS), ultra‐high performance liquid chromatography–quadrupole orbitrap mass spectrometry (UHPLC‐Q‐Orbitrap MS), and nuclear magnetic resonance (NMR) were employed to analyze and identify volatile and nonvolatile substances generated from the heat treatment of methyl cyclopropenoate standards. Based on the inferred product structures, a thermal oxidative degradation pathway for CPE‐FAs was proposed: the process initiates with a ring‐opening of the cyclopropene moiety, followed by further oxidation to yield distinct secondary oxidative products. This study provides a theoretical basis for understanding the thermal conversion mechanisms and pathways of CPE‐FAs in edible oils.