Size- and density-dependent gastric emptying of emulsion-alginate beads for tailored in vitro intestinal lipolysis.

The gastric emptying profile is essential for nutrient digestion and metabolism, and its complex relation with food structure is not well understood. Advanced dynamic in vitro digestors in combination with model food structures offer promising ways to study and control digestion in the gastrointestinal tract. In this study, the NEar Real Digestive Tract (NERDT) system is used to investigate the impact of gastric emptying on intestinal lipolysis of emulsion-alginate beads. These model food structures were 0.8-3.2 mm in size, and had different density. All particles were strong enough to resist the applied peristaltic forces and remained intact throughout gastrointestinal digestion. Particles made with higher alginate concentration settled down in the stomach due to higher density, leading to a prolonged lag time in gastric emptying. Particles with a density similar to gastric fluid mix more homogeneously and are emptied faster, depending on their as determined by gastric sieving. The half gastric emptying time (t 0.5 ) varied between 43.8 and 112 min, with higher gastric homogeneity corresponding to faster emptying, that is when particles were small and not prone to gastric sieving. The gastric emptying profiles were used to predict the intestinal substrate concentrations and FFA release profile in time. The experimental data and model showed that ∼70 % of the fatty acid release takes place in the duodenum. These insights support food matrix design for controlled digestion in the small intestine.