Influence of two lipid extraction procedures on the peroxide value in powdered infant formulas

摘要

The influence of two extraction procedures on the peroxide value (PV) of lipid extracts of powdered infant formulas (IFs) was investigated. Thirteen commercial IFs contained in their original packages were assessed after storage at room temperature for 18 months. The extraction procedures mainly differed in the extraction solvent polarity. Extraction method 1 was one of the methods more widely applied in the industry of powdered IFs. It consisted of a single extraction with a polar solvent composed of dichloromethane : methanol (2:1, v/v). Extraction method 2 consisted of disruption of the solid matrix simply by rubbing with a mortar and pestle and subsequent extraction of the lipids released with hexane, used as a non-polar solvent. The PV was contrasted with the quantitative analysis of the non-volatile lipid oxidation compounds and tocopherols. The oxidation compounds were isolated by solid phase extraction (SPE) and analyzed by high-performance size-exclusion chromatography (HPSEC) with refraction index detection. Results showed high significant differences (P < 0.0001) in the PV between the extraction methods, with lower values for method 1. However, no significant differences were found either in the levels of oxidation compounds or in those of tocopherols (P > 0.05). It was found that the lower PVs in method 1 were due to reducing substances co-extracted with the lipids by the polar solvent. Therefore, the quantitative analysis of the lipid oxidation compounds by SPE–HPSEC was more reliable for evaluation of the oxidation level in powdered IFs.