Comparative [i]in vitro[/i] dynamic digestion of powder/liquid infant formulas: characterization of structure, proteolysis and lipolysis

Digestion of nutrients is an essential function for newborn to allow normal growth and development and infant formulas remain the major source of nutrients for the neonate when breast-feeding is not possible.The objective of this study was to compare and characterize the digestion products during simulated digestion of powder(P)/liquid(L) infant formulas.Two commercial infant formulas of similar composition but in a powder or a liquid form were submitted to an in vitro dynamic digestive system. The digestion products from the gastric and intestinal compartments were characterized during 180 min by SDS-PAGE and Thin-Layer Chromatography to follow the kinetics of proteolysis and lipolysis, respectively. Changes in the structure of effluents were evaluated by confocal microscopy, light scattering and rheological methods.Results showed different structural and molecular behaviors between the 2 formulas. L had fat globules smaller than P, leading to a higher specific surface. After 30 min, protein destabilization was observed for both formulas and became definitive at 120 min. Viscosity of P and L was similar before digestion but increased dramatically for L at 120 min of gastric digestion. Overall, during the gastric phase, caseins were hydrolyzed more rapidly than the other milk proteins particularly for L and -lactoglobulin was more resistant to hydrolysis than caseins. The same behavior was observed for lipolysis kinetics with a more rapid hydrolysis of TAG for L than for P. During the intestinal phase, proteins were hydrolyzed instantaneously by the pancreatic enzymes and lipids were emulsified by bile salts, so that no difference in structure or in kinetics of hydrolysis was observed between the 2 formulas.Our results highlighted the impact of the structure of the 2 formulas on their behavior during the gastric phase that appears as a key step during in vitro digestion