Understanding how the structure of dairy matrices effects protein hydrolysis in the gastrointestinal tract

International audienceThe objective of this study is to better understand and model the effect of dairy matrix structure on the hydrolysis and transit rates of milk proteins during digestion. 4 dairy matrices having a similar composition but differing by their internal structure were manufactured: 2 solutions, 1 acid gel and 1 stirred acid gel which all contained a small amount of Cr-EDTA complexes, a non-absorbable and non-hydrolysable water soluble marker. These 4 matrices were given to six adult mini-pigs and, for each experiment, 9 samples corresponding to 8 different times after the meal ingestion and 1 time before the meal were collected after the pylori, i.e. at the stomach exit. Effluents were analysed by ELISA to determine their residual concentration in β-lactoglobulin and caseins (intact proteins and large fragments) and by atomic absorption to measure the Cr2+ concentration. Statistical analyses performed on ELISA data for proteins are presented. They allow distinguishing the gelled from the liquid matrices, the stirred acid gel being equally distributed among the two groups. A first mathematical model describing the gastric emptying of Cr-EDTA is also presented. This model provides a good fitting of the Cr-EDTA concentrations and allows estimating several unknown digestion parameters (level of gastric juice flow and half-life of the chromium complex in the stomach) with a good accuracy