Development and validation of a dynamic system for monitoring in vitro food digestion

The best model for studying food digestion remains the Human himself. An alternative to in vivo assays is to use in vitro digestion system. The complexity is to perform a device able to mimic accurately the fate of the food occurring in the human digestive tract. The objective of this work was to develop a simple and rather cheap dynamic digestion system enabling the study of the disintegration occurring in the gastro-intestinal tract of neonate and to validate it towards in vivo data. Digestion of an infant formula was studied both in vitro and in vivo using the piglet model. The formula was adapted to the energy and protein requirements of piglets. Six piglets were slaughtered 30, 90 and 210 min after the meal intake. Effluents from the different compartments of the gut were collected at these 3 time points. In parallel, the same infant formula was digested using the in vitro dynamic digestion system. The device consists in two compartments i.e. stomach and small intestine, and is computer-controlled. Milk proteolysis was followed by SDS-PAGE and ELISA both in vivo and in vitro. The validation was assessed by comparing the kinetics of residual immunoreactivity of β-lactoglobulin and caseins. Results showed a good accordance between the 2 systems of digestion. A level of in vitro/in vivo correlation was established with a correlation coefficient of 0.987. Casein content decreased rapidly during the first 30 minutes of gastric digestion. In contrast, β-lactoglobulin remained much longer intact in the stomach (120 min after ingestion). Intestinal digestion resulted in rapid and drastic hydrolysis, no more intact proteins were detected. This validation on infant formula, using the piglet model, has confirmed that this in vitro dynamic digestion system is reliable.