Inhibitory mechanism of catechins on furan formation by thermal oxidation of linoleic acid

This study systematically investigated the inhibitory effects of catechins including (-)-epigallocatechin gallate (EGCG), epicatechin gallate (ECG), (-)-epicatechin (EC), and (-)-epigallocatechin (EGC) on furan formation during thermal oxidation (150 °C, 30 min) of linoleic acid, a major unsaturated fatty acid in vegetable oils. All catechins, tested at linoleic acid: catechins molar ratios of 10:1 to 1:1, demonstrated dose-dependent suppression of furan and volatile aldehydes formation, except EC/ECG at 10:1 which promoted formation of the critical furan intermediate, (E,E)-2,4-decadienal. The inhibitory effects of the four catechins on 2,4-decadienal levels largely matched their efficacy in reducing furan generation. Among the catechins, EGCG exhibited the most potent inhibitory activity. It significantly suppressed both furan generation and the formation of the key (E,E)-2,4-decadienal intermediate during linoleic acid heating (150 °C, 0-120 min) compared to the control (P < 0.05). Mechanistic investigations revealed that EGCG reduced linoleic acid degradation by 47.3 % versus the control, as quantified by ¹H NMR analysis. Electron paramagnetic resonance (EPR) spectroscopy further demonstrated that EGCG significantly attenuated the formation of alkyl radicals, indicating interference with radical chain propagation. Crucially, liquid chromatography coupled with quadrupole time-of-flight tandem mass spectrometry (LC-QTOF-MS/MS) analysis, supported by computational modeling, confirmed the absence of covalent adduct formation between EGCG and either linoleic acid or 2,4-decadienal. These results indicate that EGCG primarily suppresses (E,E)-2,4-decadienal generation by delaying linoleic acid oxidation via quenching radical chain reactions, thereby reducing furan formation. The findings highlight the potential of catechins, particularly EGCG, for mitigating harmful thermal oxidation processes in vegetable oils during food processing.