Influence of dietary fibers on lipid digestion: Comparison of single-stage and multiple-stage gastrointestinal models

Simulated gastrointestinal tract (GIT) models are commonly used to establish the major factors influencing lipid digestion. In this study, two widely used static in vitro digestion models were compared for their ability to monitor the impact of dietary fibers on lipid digestion: a single-stage (small intestine) and a multiple-stage (mouth, stomach, small intestine) model. The impact of three dietary fibers with different electrical characteristics on the digestion of protein-coated lipid droplets was studied: cationic chitosan; anionic alginate; neutral locust bean gum (LBG). The particle size, particle charge, microstructure, rheology, and lipid digestion rate were measured. The GIT fate of the lipid droplets depended on dietary fiber type, with extensive droplet aggregation being induced upon fiber addition due to either depletion or bridging mechanisms. The microstructure and electrical characteristics of emulsions containing dietary fibers measured after the small intestine phase were fairly similar for the single- and multiple-stage GIT models, whereas the rate of lipid digestion was appreciably different. In the single-stage model the total amount of free fatty acids produced in the small intestine phase decreased in the following order: control (83%) ≈ LBG (87%) > chitosan (72%) > alginate (59%). However, in the multiple-state model the total amounts of free fatty acids produced were fairly similar for all fibers (83–94%). This study highlights the importance of selecting an appropriate simulated GIT model to examine the potential gastrointestinal fate of food, pharmaceutical, and feed systems.