Monitoring of 2,4-decadienal in oils and fats used for frying in restaurants in Athens, Greece

Some frying by-products of medium polarity, so-called medium-polarity materials (MPM), produced during domestic deep-frying of French-fried potatoes in edible vegetable oils, have recently been isolated and linearly correlated to % total polar materials and % polymerized triglycerides. The in vitro oxidation of low-density lipoproteins in a dose-dependent manner by MPM has also been reported. In the present study, the MPM constituents were identified after extraction of MPM from the oils, subsequent purification by RP-HPLC, and GC-MS analysis. The main constituent of MPM was trans, trans-2,4-decadienal, a compound that has previously been reported to be formed during peroxidation of linoleic and arachidonic acid. 2,4-Decadienal was also quantified in oils and fats used for frying in restaurants in Athens, Greece, by direct injection of oil sample solutions in HPLC. For the most commonly used frying oils, 2,4-decadienal concentration ranges were 0.3-119.7 mg/kg for sunflower oil, 13.3-92.7 mg/kg for cottonseed oil, 4.1-44.9 mg/kg for palm oil, and 2.0-11.3 mg/kg for vegetable cooking fats. Considering the common catering practices of frying, 2,4-decadienal was more likely to be found in sunflower oil after deep-frying of potatoes. Comparing the amounts of this aldehyde found in oils from restaurants to the amounts previously found for domestic frying (up to 30 mg/kg after the 8(th) successive frying session in sunflower oil), the probability of consuming a level of 2,4-decadienal in restaurant-prepared food that is higher than the level in home-fried food was determined to be approximately one third.