Effect of storage time and temperature on parent and oxygenated polycyclic aromatic hydrocarbons in crude and refined vegetable oils.

Changes in polycyclic (PAH) and oxygenated (OPAH) aromatic hydrocarbon concentrations in vegetable oils during storage for 270days at 25°C or 4°C were investigated. The concentrations of OPAHs and PAHs increased with storage time. The increase in PAH concentration was mainly caused by light PAHs. Total PAH concentrations increased from 33.11-36.77μg/kg to 45.12-58.04μg/kg in 26 crude oil samples, while those in 26 refined oil samples increased from 16.52-20.02μg/kg to 25.73-40.01μg/kg. Acid value (AV) and peroxide value (POV) also showed an increase during the storage process from 0.08-0.92mg/kg to 0.33-2.98mg/kg, and from 0.08-0.12mmol/kg to 0.33-3.45mmol/kg in 52 tested oils, respectively. AV and POV were within the regulatory limits of China after storage for 270days. However, concentrations of 16 PAHs in all tested oils exceeded 25μg/kg. The results indicated PAHs and OPAHs formation was better inhibited in oils stored at lower temperature.