Unexpectedly High Levels of Environmentally Persistent Free Radicals in Barbecued Foods: An Overlooked Source

Environmentally persistent free radicals (EPFRs) are recognized oxidative stressors, but existing research focuses predominantly on inhalable particles. Thermally carbonized foods represent a potentially major, yet unexplored, dietary EPFR pathway. Here, we quantified EPFRs in commercial barbecued foods and conducted controlled experiments to identify thermal, heating-source, and matrix factors governing their formation. Barbecued foods exhibited high EPFR levels (1.7 × 1016–6.3 × 1018 spins/g), 2–3 orders of magnitude higher than previously reported values for fried/steamed foods. Controlled experiments revealed EPFR formation as a nonlinear thermal process governed mainly by temperature and food matrix with yields increasing up to 3-fold from 80 to 200 °C. Heating-source effects were matrix-dependent, as charcoal grilling produced ∼9-fold higher EPFRs of (3.6 ± 0.4) × 1018 spins/g than electric heating in lipid-rich meats, but only ∼2-fold higherlevels in vegetables, indicating matrix-driven carbonization and combustion-derived contributions. Oxidative potential correlated positively with EPFRs and polycyclic aromatic hydrocarbons rather than trace elements, suggesting EPFRs and coformed redox-active organic mixtures drive oxidative burden. Combined with a dietary survey, the estimated burden is 2.1 × 1020 spins per barbecued meal for a 65 kg adult. These findings highlight thermally carbonized matrices as under-characterized EPFR sources with significant dietary implications.