Abstract

Comparative Evaluation of Diagnostic Tools to Characterize Lipid Oxidation of PUFA-Enriched Infant Formulas

Caroline Siefarth, Food Engineer & Research Associate, University of Erlangen Nuremberg

Clinical studies have revealed positive effects of polyunsaturated fatty acids (PUFAs) on the visual and cognitive development of new-borns and infants. Thus, over the past years infant formulas (IFs) have increasingly been enriched with ?-3 and ?-6 fatty acids. However, due to the unsaturated nature of PUFAs they are very susceptible to lipid autoxidation, which may lead to the development of unpleasant or even aversive off-flavours in PUFA-enriched IFs. The industry is currently in search of analytical tools to monitor autoxidation in its early stages with respect to quality control and product development of PUFA-enriched IFs. In this context, three different diagnostic tools on monitoring primary and secondary lipid oxidation markers were comparatively investigated. Two-dimensional high resolution gas chromatography mass spectrometry/olfactometry (2D-HRGC-MS/O) was used to screen odour-active secondary oxidation products. In contrast, two standard operating tools in monitoring autoxidation were performed: the photometrical determination of lipid hydroperoxides and of conjugated dienes. Multi-dimensional GC-MS/O proved to be a very sensitive tool to monitor lipid oxidation in IF powders immediately after production and in its early stages (0-8 weeks). Besides classical monitoring of saturated alkanals, it was possible to confirm further secondary oxidation markers with high diagnostic value like alkenals, alkadienals, alkenones and alkadienones. The formation of primary lipid oxidation markers via the photometrical methods could also reveal autoxidation processes in the IF powders; however, longer time intervals were necessary to obtain significant results.