Factors affecting the polycyclic aromatic hydrocarbon content of cereals, fats and other food products.

Factors affecting polycyclic aromatic hydrocarbon (PAH) concentrations in oils and fats, cereals and related foodstuffs have been investigated. Levels of PAHs were low in retail fish and animal-derived oils and fats, such as butter, where the mean benzo(a)pyrene concentration was 0.06 microgram/kg. Higher and more variable amounts were present in retail vegetable oils for which the mean level of benzo(a)pyrene was 1.29 micrograms/kg. Margarine was the major dietary source of PAHs in the oils and fats total diet group accounting for 70% of the benzo(a)pyrene intake from these commodities. The levels of benzo(a)pyrene were less than 0.1 microgram/kg in white flour and similar amounts were found in bread showing that PAHs are not formed to any significant extent during baking of bread. Higher concentrations of up to 2.2 micrograms/kg benzo(a)pyrene were detected in cereal-derived products containing higher levels of edible oils such as pudding-based desserts, biscuits and cakes. The presence of vegetable oils as an ingredient also appeared to increase PAH levels in infant formulae as the mean benzo(a)pyrene content of 0.49 microgram/kg was four times higher than that found in skimmed milk. The mean value in the feed, after reconstituting the formulae with water, would however have been less than 0.1 microgram/litre. Investigations of rape seed drying showed no increase in any PAHs when cold, or electrically-heated air was used. Combustion gas drying had no effect for the larger PAHs such as benzo(a)pyrene but caused mean increases of between 41% and 126% for fluoranthene, pyrene and chrysene. These increases did not correlate with reductions in moisture content of the rape seed implying that the combustion conditions were more important to PAH contamination than the degree of exposure to combustion gases. Concentrations of these three PAHs and also benz(a)anthracene were all significantly reduced by up to a factor of five when crude oils were refined suggesting that carefully controlled direct drying need not contribute PAHs to refined oils and fats.