Changes in PAHs levels in edible oils during deep-frying process

• Changes in the PAHs in four types of edible oils during the deep-frying process were examined.
• Four types of fresh edible oils contained PAHs, particularly low-ring PAHs.
• The PAHs in the edible oils increased with increasing deep-frying time.
• B[a]P and ∑4PAH significantly exceeded the regulation limits.

Changes in the 16 PAHs in rapeseed, soybean, peanut and olive oil during deep-frying were examined to evaluate PAH levels in edible oils and the effects of deep-frying time. Chicken nuggets and potatoes were deep-fried in four types of oil for 15, 30 and 45 min. PAH concentrations were quantified via high-performance liquid chromatography (HPLC). The results show that all four fresh (unused) edible oils contain PAHs (189.9–2754.8 μg/kg) and mainly low-ring (2- to 4-ring) PAHs. PAH concentrations in the edible oils increased with increasing deep-frying time, especially among the high-ring (5-ring and above) PAHs. The mean values of high-ring PAHs (5-ring and above) in the samples deep-fried for 45 min were 1.9-fold higher than the oil samples that were deep-fried for 15 min and 31.5-fold higher than the levels for the fresh oils. The mean concentrations of benzo[a]pyrene in the deep-fried peanut and olive oils were 6.1- and 5.2-fold, respectively, the control value established in China (10 μg/kg). Average levels of ∑4PAH (consisting of benzo[a]anthracene, chrysene, benzo[b]fluoranthene, and benzo[a]pyrene) for the two deep-fried oils also exceeded the maximum permitted limit (10 μg/kg) set by the European Union (9.2- and 6.8-fold higher, respectively). At present, regulations imposed in China limit only concentrations of benzo[a]pyrene. The results of this study show that more standards and regulations on PAHs in edible oils must be established. In addition, the repeated use of edible oils must be avoided.