The relation between the determinable quantities of volatile N-nitroso compounds and the peroxide number in soya bean oil.

Comparative studies of soya bean oil with and without addition of N-nitroso compounds (NDMA and NDEA) at different hydroperoxide concentrations have shown that the determinable quantities of substances having the retention time of N-nitroso compounds in soya bean oil and of nitrosoamines added to the oil are dependent upon the peroxide number. The determination was carried out by gas chromatography (nitrogen detector, nitrogen-sensitive, flame-ionization detector) prior to and following irradiation with UV light (360 nm). When the peroxide number was above 4, the determinability and the recovery were reduced by more than 60 per cent. In advanced autoxidation and after reduced recoveries, large amounts of NMDA and NDEA may be encountered for a short time. A possible linkage between N-nitroso compounds and peroxide is discussed. Comparative investigations of soya beans, crude oil, intermediates and commercially available steamed oils have revealed that the concentrations of the compounds with NDMA and NDEA properties in crude oil (peroxide number about 3) is higher than in soya beans. The recovery of these compounds is very poor in intermediate products with high peroxide numbers (about 5 to 9). However, N-nitroso compounds can be demonstrated in commercially available oils treated with steam (peroxide number about 0.7), although to a lesser extent than in crude oil.