Résumé
The study of digestion is difficult to conduct in humans as trials imply technical, ethical and financial constraints. In vitro alternatives are thus used for screening different foods and for a better understanding of digestive kinetics. To date, there is no physiologically pertinent model of in vitro static digestion at the infant stage. Thanks to an extensive literature review of the in vivo infant digestive conditions, an infant gastro-intestinal static in vitro model was developed. Based on the in vivo half-time emptying of infant formula, digestive conditions were set up for the gastric and intestinal phases. The oral phase was not considered due to the infant formula nature. The following parameters were determined: pH, ratio of meal to secretions, enzyme units of pepsin and gastric lipase (added as rabbit gastric extract) and pancreatin (porcine source). The molarity of biliary salts was also considered. Each digestion step (gastric and intestinal) lasted 60 min. Three digestion replicates of a commercial infant formula were conducted. The same formula was subjected to the adult standardised protocol of in vitro static digestion in three replicates in order to compare the digestive kinetics and endpoints. Gastric and intestinal digesta were sampled regularly. Proteolysis kinetics was followed by SDS-PAGE and lipolysis kinetics by Thin Layer Chromatography. As a result, the digestive kinetics of infant formula were impacted by the physiological stage and the degree of hydrolysis differed according to the stage likely due to the reduced level of enzymes in the infant model. This model could be used for infant formula from different milk source as well as for human milk as long as the half-time emptying is known and the digestive conditions subsequently determined.