Acid and rennet gels exhibit strong differences in the kinetics of milk protein digestion and amino acid bioavailability

This study aimed at determining the kinetics of milk protein digestion and amino acid absorption after ingestion by six multi-canulated mini-pigs of two gelled dairy matrices having the same composition, similar rheological and structural properties, but differing by their mode of coagulation (acidification/renneting). Duodenal, mid-jejunal effluents and plasma samples were collected at different times during 7 h after meal ingestion. Ingestion of the acid gel induced a peak of caseins and β-lactoglobulin in duodenal effluents after 20 min of digestion and a peak of amino acids in the plasma after 60 min. The rennet gel induced lower levels of both proteins in the duodenum (with no defined peak) as well as much lower levels of amino acids in the plasma than the acid gel. Plasma ghrelin concentrations suggested a potentially more satiating effect of the rennet gel compared to the acid gel. This study clearly evidences that the gelation process can significantly impact on the nutritive value of dairy products.