Towards infant formulas mimicking human milk structure and gastric digestion

Milk lipids supply most of the calories necessary for newborn growth in maternal milk or infant formulas. The chemical composition of infant formulas has been optimized but not the structure of the emulsion. There is still a major difference between native emulsions of milk fat globules (4 μm) and processed submicron emulsions with neoformed interface (0.5 μm) in infant formulas. This structural difference may modify the kinetics of digestion and disintegration of the emulsion in the digestive tract of the newborns. To check this hypothesis, several model infant formulas representative of native, homogenized, homogenized/pasteurized milk emulsions, commercial infant formula or Human milk were subjected to semi-dynamic or dynamic in vitro digestion mimicking the conditions reported in newborns [1,2]. In the gastric phase, native emulsions were lipolyzed and proteolyzed slower than processed model or commercial infant formulas. The difference in initial structure was maintained during the gastric phase of digestion which was dominated by acid aggregation. Our findings indicate that the surface of the droplets in the infant formula is the key parameter to control gastric lipolysis kinetics, the degree of gastric lipolysis and also the pattern of released fatty acids. This parameteralso indirectly controls gastric proteolysis kinetics since adsorbed proteins are hydrolyzed faster than solubilized proteins. These differences in gastric digestion may have important physiological implications and provide important new data to review and partly explain the difference in gastric emptying between human milk and infant formulas. The results of this study will be useful to food scientists and infant food manufacturersas they provide evidence for the direct influence of the structure of the emulsion in neonatal gastric digestion and underline the need for developing soft processes with minimal impact on milk emulsion structure in the near future.