In vitro digestion of pectin- and mango-enriched diets using a dynamic rat stomach-duodenum model

In this study we investigated the in vitro digestive behaviors of starch-based diets enriched with soluble fiber (pectin) and fruit powder (mango) varying with dry matter contents using a dynamic rat stomach and duodenum model. The changes in pH with respect to digestion time, gastric emptying, starch and protein hydrolysis as well as rheological and microstructural properties of the gastric and duodenal digesta were investigated. The effects of porcine gastric mucin on digestion were studied as well. The results showed that gastric digestion and emptying rate were decreased with increasing dry matter content of the diets. Both the dynamic and steady shear viscosity of the duodenal digesta was lower than the gastric digesta due to hydrolysis of starch and protein as well as dilution by added digestive juice. With the same dry matter content (20.35%), the rates of gastric emptying as well as starch and protein hydrolysis were higher in the control and mango diets compared to the pectin diet, illustrating the complex relationships among rheology, soluble dietary fiber and digestion. The addition of gastric mucin could delay the rates of gastric digestion and emptying by increasing digesta viscosity. The study emulates the complexity of heterogeneous diets during simulated gastric and duodenal digestion and suggests that the viscosity generated by either addition of mucin on the diet or naturally exerted by e.g. pectin could be the rate limiting factor for both gastric emptying and hydrolysis of starch and proteins.