Impact of food viscosity on in vitro gastric emptying using dynamic and semi-dynamic models

Viscosity has been shown to affect food breakdown and nutrient release in the gastrointestinal tract, and the subsequent postprandial glycaemic response and satiety. However, the correlation between food viscosity and gastric emptying is not fully understood. This study investigated the in vitro gastric emptying behavior of peanut butter with different viscosities using semi-dynamic and the artificial gastric digestive system (AGDS) models. Results from both digestion models showed that high viscosity peanut butter had a slower pH decrease, higher buffering capacity, slower phase separation of gastric chyme and less protein hydrolysis and lipid digestion than the control and low viscosity groups. However, the AGDS displayed slower gastric emptying rate, smaller chyme particle size and less proteolysis than the semi-dynamic model, particularly in the high-viscosity group (e.g. ∼60% of gastric emptying rate for AGDS and ∼20% for semi-dynamic model at 120 min), due to the different mechanical shearing forces and gastric emptying patterns in these two models. This study demonstrated the role of food viscosity on the gastric emptying process, and it also suggested that viscosity should be taken into account when designing future functional foods with particular structure.