4-hydroxy-2-alkenals in polyunsaturated fatty acids-fortified infant formulas and other commercial food products.

4-Hydroxy-2-hexenal (HHE) and 4-hydroxy-2-nonenal (HNE) were determined using selected ion-monitoring gas chromatography-mass spectrometry (GC-MS) in 56 kinds of commercially available PUFA-fortified foods including infant formulas and baby foods. HHE and HNE, each specifically coming from the oxidation of n-3 and n-6 polyunsaturated fatty acids (PUFA), were observed at <10-77 and 41-132 microg kg(-1) in the infant formulas (n = 12) and at <10-52 and 36-116 microg kg(-1) in the baby foods (n = 7), respectively. 4-Hydroxy-2-alkenals in infant formulas and baby foods were further determined at 10 and 30 days after opening in an attempt to examine the time dependence of the levels of 4-hydroxy-2-alkenals. The values of HHE and HNE had increased appreciably to <10-220 and 79-792 microg kg(-1) in infant formulas and to <10-112 and 135-572 microg kg(-1) in baby foods, respectively, at 10 days and decreased, although statistically not significant, in most of the tested samples after 30 days, which suggested that the reactive compounds might interact with other constituents like proteins in the samples to form adducts or be decomposed with time. Based on the current study, it was calculated that 3-month to 1-year-old babies maintained exclusively on these commercially available PUFA-fortified infant formulas or baby foods could be exposed to a maximum of 20.2 microg kg(-1) body weight day(-1) of 4-hydroxy-2-alkenals, which is two orders of magnitude higher than the exposure of Korean adults estimated in a previous study of the authors' (2005). The present study may trigger future studies investigating the physiological influence of 4-hydroxy-2-alkenals originating from the diet on man at an early stage of development.