From bolus to digesta: How structural disintegration affects starch hydrolysis during oral-gastro-intestinal digestion of bread

Abstract

This study aimed to understand the role of structural disintegration on starch hydrolysis during in vitro digestion. In particular, the impact of in vitro oral processing method (i.e. cutting, cut-and-pestle, blending and grinding) and bread structure (i.e. baked bread, steamed bread and baguette) were investigated. Structural disintegration and starch hydrolysis of bread bolus through oral, gastric and intestinal digestion were characterised. The average starch hydrolysis was 9.5%, 49% and 68% at the end of oral, gastric and intestinal digestion, respectively. The average particle size was decreased from 20 mm2 in the bolus to 109 μm and 73 μm in the chyme and digesta, respectively. Small particle size promoted saliva impregnation and enhanced particle cohesion. Steamed bread was less resistant to structure disintegration, especially during the early stage of gastric digestion. The impact of oral processing was diminished over the digestion process, while the impact of bread type became more predominant. Bread structure played an important role in both gastric and intestinal digestion. The denser bread structure of steamed bread led to a less degree of starch hydrolysis (63%) at a slower rate as compared to the baked bread and baguette (68 and 73%). Results of this study revealed the importance of bread structure and its transformation during in vitro oral processing on the physical and chemical digestion of bread at oral, gastric and intestinal phases.