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.

The changes in physical, rheological and enzyme-digestive behaviours of cooked white and brown rice, with similar amylose content, were investigated using a dynamic in vitro rat stomach (DIVRS) model and a static soaking method. The brown rice had a higher resistance on disintegration and lower gastric emptying rate with 53% of the brown rice particles retained in the stomach at the end compared to 32% for the white rice. Furthermore, the release rate of maltose from the starch hydrolysis was higher in the white rice throughout the digestion suggesting the lower glycemic potency of the brown rice. These differences could be contributed from the rigid bran layer in the brown rice which would inhibit the moisture absorption into rice kernels, limit textural degradation, and generate higher gastric digesta viscosity leading to lower mixing and mass transfer efficiency. This study suggests that the structural difference could affect physiochemical properties during gastric digestion.

No abstract

Delocalisation and transfer of electrons in the formed IPr–(Ru) synergistically yields a significant improvement in activity with respect to its counterpart.