Key to Promoting Polycyclic Aromatic Hydrocarbons Generation in Lipid Thermal Reactions: Free Radicals Originating from Lipid Hydroperoxides.

Prior research linked polycyclic aromatic hydrocarbons (PAHs) formation to lipid oxidation. However, the specific oxidation products responsible for PAHs generation remain unclear. In this study, the thermal reaction systems of linoleic acid (LA)-LA hydroperoxide (LA-OOH) (primary oxidation product) and LA-secondary oxidation product were constructed to compare the effects of LA-OOH and secondary products on PAHs generation. Results showed that PAH4 production in the LA-LA-OOH (40%) group increased by 35.2 to 42.4% compared to LA, while secondary product addition with highest concentrations to LA only increased PAH4 by 5.4 to 33.8%, indicating LA-OOH had a significantly higher promoting effect on PAHs. LA-OOH decomposition produced radicals and secondary products, with radicals being the primary driver of PAHs formation. These radicals promoted PAHs formation through two mechanisms: carbon-centered radicals cyclized themselves to form intermediates and a reduction of activation energy for chain scission and dehydrogenation. Thus, controlling radicals from primary oxidation products is crucial for reducing PAHs in food.