Study on the digestion of milk with prebiotic carbohydrates in a simulated gastrointestinal model

The behaviour of oligosaccharides from lactulose (OsLu) included with milk was examined during in vitro gastrointestinal digestion using the Infogest protocol as well as some small intestine rat extract. The digestion was compared with commercial prebiotics GOS and Duphalac®. Electrophoretic analysis demonstrated that the prebiotic carbohydrates did not modify the gastric digestion of dairy proteins. Similarly, no significant effect of gastrointestinal digestion was shown on the prebiotic studied. In contrast, under the intestinal conditions using a rat extract, the oligosaccharides present in OsLu samples were less digested (<15%) than in GOS (35%). Moreover, lactulose was more prone to digestion than their corresponding trisaccharides. These results demonstrate the limited digestion of OsLu and their availability to reach the large intestine as prebiotic.