Sterol oxidation in ready-to-eat infant foods

The content of sterol oxidation products (SOP) in ready-to eat infant foods was evaluated by thin-layer chromatography-gas chromatography (TLC-GC). Two different flavor (honey or fruits) liquid infant foods prepared with milk and cereals, were subjected to various storage periods (0, 2, 4, 7 and 9 months) at 25ºC. Lipids were extracted, subjected to cold saponification, purified by silica solid-phase, silylated and analyzed by GC. Their identification was further confirmed by TLC and GC-mass spectrometry (GC-MS). The main SOP found were the 7-keto derivatives of all sterols analyzed, being the 7-ketositosterol the most abundant one (0.33 mg/kg of sample). However, alpha- and beta-epoxy derivatives of both sitosterol and cholesterol, as well as cholestanetriol, were detected in the two types of samples. The extent of cholesterol oxidation (0.04%) was twice as much that of phytosterols (0.02%). However, no significant differences in the sterol and SOPs content (average value of 16.4 mg/100g sample and 1.29 mg/kg sample, respectively) of the two infant food formulations, were found. In addition, no significant effects of storage on the SOPs content of both infant food formulations, were detected.