Résumé
Infancy period is a key window of development during which the requirements in lipids and more particularly in long-chain polyunsaturated fatty acids are specific. In order to abide by the recommendations, European regulation now requires a fortification of infant follow-on formulas (IFF) with docosahexaenoic acid (C22:6, DHA) which strongly impacts their oxidative stability. The aim of this study was to optimize the structure and formulation of DHA-enriched IFF in order to improve their lipid profile and oxidative stability. To do so, a model IFF representative of marketed products was formulated and declined by varying the saturated fatty acids sources (refined (POM) or unrefined (RPOM) palm oil, coconut oil (COM), and dairy fat (DFOM)), the emulsifiers (soy lecithin or dairy phospholipids (DPL)) and the structure (droplet size). These model IFF were submitted to an accelerated storage test of 20 days at 40°C during which peroxide values (PV), tocopherols, vitamin A, and fatty acids profiles were monitored. Despite the addition of DHA, all model IFF had quite good oxidative stability with PV lower than 10 meqO2/kg of lipids until 9 days of storage. DFOM and POM had equivalent kinetics of PV increase and tocopherols degradation. Moreover, no significant differences were observed between these two IFF regardless of droplet size (0.4 or 0.7 µm). RPOM was more stable than POM, very likely due to its higher carotenoids content. Regarding emulsifiers, DFOM-DPL (stabilized with DPL) had a PV twice lower than POM (stabilized with lecithin) at 20 days and a tocopherols degradation of 67.5% vs 88.8% for POM. This result translates a more important resistance to oxidative degradation of DFOM-DPL. This favorable effect was even reinforced for smaller droplet sizes. The introduction of dairy lipids but also of carotenoids in DHA-enriched IFF composition are interesting levers of stabilization. Moreover, dairy lipids lead to a more complex lipid profile and a higher content of short and medium-chain saturated fatty acids which is beneficial for infant nutrition.