Résumé
Vitamin A deficiency is the most widespread micronutrient deficiency worldwide leading to reduced immunity, enhanced morbidity and potentially to children blindness (250,000 to 500,000 children yearly; WHO). To ensure an adequate vitamin A status, infant follow-on formulas (IFF) are usually supplemented with the addition of premixes containing different chemical forms of vitamin A. However, vitamin A is very sensitive to degradation which makes its inclusion in food matrices very challenging. This study aimed at investigating the vitamin A stability in IFF depending on the pressure of the homogenization process applied and on the chemical form of vitamin A. For this propose, a model IFF representative of commercialized products was formulated and processed at two different homogenization pressures and supplemented with 3 different chemical forms of vitamin A or its precursor (retinol, retinyl acetate or carotenoids). Loss of vitamin A in the IFF was assessed either before or just after the high pressures homogenization step or after an accelerated storage test of 20 days at 40°C. Considering loss during processing, the homogenization pressure had, as expected, a strong impact on vitamin A stability with loss of 2.5% at lower pressure (100/30 bars, 8 passes) versus 10% at higher pressure (350/40 bras, 8 passes). This most important degradation of vitamin A content for higher homogenization pressure (needed for instance to obtain 0,4 µm average droplet size) was very likely explained by higher shearing forces leading to local heating of molecules. Moreover, chemical form of vitamin A used for fortification also significantly influenced vitamin A loss, with 44.1% of degradation for IFF fortified with retinyl acetate versus 68.5% for IFF fortified with retinol after 20 days storage. This result points out a more important sensitivity to degradation of retinol very likely due to its higher hydrophilicity in agreement with data already evidenced in other matrices by the Scientific Committee on Consumer Safety (2016). The results also indicated that the presence of carotenoids and especially β-carotene led to a stabilization effect, only 40.7% of vitamin A was degraded after 20 days of storage in the presence of carotenoids versus 75.9% in the absence of carotenoids. More generally, the presence of carotenoids provides a better resistance to lipid oxidation due to its synergetic effect with vitamin E (Schroeder et al. 2006). This study highlights that despite the important sensitivity of vitamin A, a good knowledge of its reactivity during processing and selection of chemical form and potential synergy with other compounds can improve its stability in IFF emulsions.