Incorporation of the toxic aldehyde 4-hydroxy-2-<Emphasis Type="Italic">trans</Emphasis>-nonenal into food fried in thermally oxidized soybean oil

The toxic aldehyde 4-hydroxy-2-trans-nonenal (HNE) is an oxidation product of linoleic acid and is formed during the thermal oxidation of soybean oil at frying temperature. This investigation was conducted to determine whether HNE would be incorporated into food fried in thermally oxidized soybean oil. Commercially available liquid soybean oil was heated at 185°C for 5 h prior to frying uniform pieces of potato (1×0.5×7 cm). The oil was sampled prior to and after frying and was analyzed for the presence of HNE and other polar lipophilic aldehydes and related carbonyl compounds by HPLC. The oil was also extracted from the fried potato pieces and was analyzed identically to the frying oil. HNE was found to be a major polar lipophilic compound in the thermally oxidized frying oil, as previously published by this laboratory, and in the oil extracted from the fried potato. Similar concentrations of HNE were found in the oil prior to and after frying and in the oil extracted from the fried potato (57.53±16.31, 52.40±6.10, and 59.64±11.91 mg HNE per 100 g oil, respectively). These results indicate that toxic HNE was readily incorporated into food fried in thermally oxidized oil; extensive consumption of such fried foods could be a health concern.