In vitro measurements of luminal viscosity and glucose/maltose bioaccessibility for oat bran, instant oats, and steel cut oats

Abstract Three commercially available oat products—instant oats, steel cut oats, and oat bran—were studied using the TNO Intestinal Model-1 (TIM-1) coupled with fluorescence spectroscopy and molecular rotors to evaluate carbohydrate digestion and in vitro gastric viscosity as a function of time. A proportional relationship between total bioaccessible sugars and the concentration of available carbohydrates was observed for the different oat-based foods. The rate of starch digestion was greatest for instant oats and lowest for steel cut oats. β-glucan, starch, and total carbohydrate concentrations were proportional to the initial gastric viscosity. Overall, gastric viscosity differed considerably between samples. Instant oat and oat bran viscosities were highest at the onset of digestion and decreased with time, whereas the viscosity of steel cut oats at the onset of digestion was the lowest viscosity observed, increasing with time. These findings suggest that modification of food form and formulation during processing alters sugar bioaccessibility and luminal viscosity.