Gastric viscosity and sugar bioaccessibility of instant and steel cut oat/milk protein blends

Milk protein concentrate (MPC; 0 g, 5 g, and 10 g) was added to two commercially available oat products (instant oats and steel cut oats) to examine how MPC addition, and consequent changes in meal formulation, manipulates both gastric lumen viscosity and intestinal carbohydrate-digestion kinetics, in vitro. We used the TNO Intestinal Model-1 (TIM-1) to simulate gastrointestinal digestion of the oats-based meals. Meals containing 5 g or 10 g MPC yielded significantly less total bioaccessible sugar compared with those containing 0 g MPC, while the rate of starch digestion was significantly higher in meals containing 5 g or 10 g MPC. The TIM-1 was coupled with fluorescence spectroscopy and a luminescent molecular rotor to report changes in gastric viscosity in situ, showing that the gastric viscosity was higher in the meals containing MPC. Those findings suggest that MPC in oats-based meals significantly modifies the kinetics of carbohydrate digestion and increases gastric viscosity.