MRI monitoring of digestion mechanisms at the scale of a food piece: proof of concept with bread

Abstract

To improve our understanding of gastrointestinal digestion of solid foods, spatially resolved insights into disintegration mechanisms at the particle level are needed. Magnetic resonance imaging (MRI), despite its non-invasive and multiscale capabilities, remains underexploited for such purposes. This study pursued two objectives: (1) to develop an MRI-compatible miniaturized setup for static in vitro oral–gastric–intestinal digestion, and (2) to apply this system to investigate online the digestion of a bread piece measuring a few millimetres using MRI (UTE 3D morphometric imaging and T₂ mapping), supplemented by chemical analyses of starch and protein hydrolysis. The setup comprises a circulation loop of the digestion fluid, linking an MRI-compatible digestion cell to a remote pH-stat system, which enables real-time control of temperature, pH, enzyme addition, and sampling. MRI results correlated well with peptide and polysaccharide release kinetics in the digestion fluid. UTE 3D imaging showed stable bread volume during gastric digestion, followed by volume loss, surface roughening, and fluid ingress into pores during intestinal digestion, consistently with gluten hydrolysis. T₂ analysis distinguished more mobile water in the pores and less mobiles ones in bread. An increase in the amount of more mobile protons suggested erosion-driven exposure and internal enzymatic attack. The release of starch hydrolysis products was shown to be independent on the breakdown of the gluten network and could be monitored with T₂ in the digestion fluid. In conclusion, this MRI-compatible setup enables time-lapse, submillimetric resolution monitoring, offering valuable insights into bread piece digestion, and could be adapted to various solid food matrices.