In vitro digestion of bread: How is it influenced by the bolus characteristics?

This study aimed to understand the impact of in vitro oral processing methods on bolus formation and the kinetics of starch hydrolysis of refined white bread during in vitro gastrointestinal digestion. Four in vitro oral processing methods (i.e. cut, cut-and-pestle, blend and grind) were performed at two levels of disintegration (less and more intensive) and compared with human mastication. Boluses prepared using the in vitro methods had a larger particle size (20-69 mm2 vs 14 mm2 ), a higher moisture content (64-68% vs 47%), a softer texture (1.3-2.3 N vs 6.3 N) and a less adhesive surface (0.3-1.0 vs 1.6 N•s) as compared to the in vivo masticated ones. Moreover, in vitro prepared blouses were digested more rapidly than in vivo masticated ones during the stimulated intestinal digestion from 150 min onwards, with a higher hydrolysis rate (0.011-0.012 mg/ml • min vs 0.010 mg/ml • min) and a higher equilibrium concentration of reducing sugar (5.5-6.3 mg/ml vs 4.9 mg/ml). Among all the in vitro methods, the blending and grinding methods produced boluses that most closely resemble the in vivo masticated ones in terms of their physical characteristics. The blending method also produced boluses having the highest amount of reducing sugar released (6.32 mg/ml). The amount of reducing sugar present in the PBS buffer outside the dialysis tube might be controlled by the diffusion efficiency at the beginning of the digestion (≤120 min) and then be largely influenced by the particle size of the bolus in the latter stage of the digestion. This article is protected by copyright. All rights reserved.