PAH-enriched and oxidized fatty co- and by-products from the food chain used in animal feedings: effects on the trans fatty acid and conjugated linoleic acid contents of poultry and rabbit

The aim of this study was to evaluate the effect of polycyclic aromatic hydrocarbon (PAH)-and oxidation product-enriched diets on the content of TFA and conjugated linoleic acid (CLA) isomers in meat and liver of both poultry and rabbits. The enriched feedings were prepared with four preselected fatty co-and by-products that contained low and high levels of PAH (acid oils from chemical refining of olive oil and olive pomace oil, respectively) and low and high levels of lipid oxidation products (sunflower-olive oil mixture (70:30, v/v), before and after commercial frying process), so as to obtain single feedings with three enrichment degrees (high, medium and low) of the compound of interest. This experimental set-up is a part of a large, collaborative European project (http://www.ub.edu/feedfat/), where other chemical and health parameters were assessed. Lipids were extracted, methylated with diazomethane, then transmethylated with 2N KOH/methanol and analyzed by GC and silver-ion TLC-GC. TFA and CLA were determined in the fats, feedings, meat and liver of both poultry and rabbit. In general, the level of TFA in meat and liver mainly varied according to those originally found in the fats added to the feeds and the corresponding feeds. In fact, TFA contents were higher for the “OXIDATION” trial than for the “PAH” one. However, TFA accumulation was different for the two animal species, as well as for the two types of tissues. The level of TFA in poultry meat and liver was about 3 and 1.5-3 times higher than in rabbit meat and liver, respectively. The amount of TFA in poultry meat was 2-2.5 times higher than in liver, whereas rabbit meat contained about half the TFA found in liver. No CLA isomers were detected in both chicken and rabbit meat and livers, because they were already absent in the various feeds.