Effect of cooking on chemical contaminants in food. Meat as example

Recent chemistry and food toxicology research suggests that just knowing the level of contamination of a farmed product is not sufficient to assess its impact, as there are certain food processing operations, like cooking, that may significantly modulate the chemical risk to the endconsumer. We studied the effect of pan-frying on the main chemical contaminants potentially found in meat. Working on meat samples purposely infected with diverse contaminants, we profiled pre-cooking and post-cooking mass balances using multi-residue analytical methods run by the National Reference Laboratories for antibiotics and heavy metals and by the INRA Livestock Products Quality research unit for pesticides and organic environmental micropollutants. The phenomena observed were then validated on meat samples naturally contaminated during the animal’s on-farm life.

RESULTS
The study revealed distinct effects of cooking according to the types of chemical contaminants analyzed. Whereas pan-frying had no significant effect on in-meat dioxin and heavy metal contents, higher-intensity pan-frying led to higher losses of polychlorinated biphenyls (PCBs), antibiotics and pesticides, which could be attributed to the mechanical expelling of cooking juices and/or to thermal degradation processes. To further investigate where these losses actually came from, heat sensitive target contaminants were radiolabelled and spiked into the meat before cooking. We then tracked these compounds, along with any degradation products, which we also labelled, during the cooking process. A study led in collaboration with the TOXALIM unit and the ANSES [French food safety and food hygiene agency] at Fougères on two radiolabelled antibiotics showed that sulfamethoxazole thermally degraded into five degradation products, which were then structurally identified using nuclear magnetic resonance and mass spectrometry.

We also managed to model the modulatory effects of pan-frying on PCBs in order to assess and compare the risks tied to eating conventionally-farmed versus organically-farmed meat.