Suivi multi-échelle par RMN des transferts d'eau dans des produits à base d'amidon

Abstract

International audienceNuclear magnetic resonance spectroscopy (NMR) and magnetic resonance imaging (MRI) are non-invasive and non-destructive methods giving access to the water mobility in porous and heterogeneous media at various scales. The first one is based on the measurement of relaxation times (T1 and T2) related to the molecular mobility more or less impacted by the sample composition, its microstructure, chemical and diffusional exchanges between protons and molecules, respectively 1. In this context, the 2D NMR, based on a joint observation of T1 and T2, has been shown to be very efficient to monitor the water transfers and the starch changes when starchy products were heated 2. A complementary approach consists in using MRI (or microimaging) to study swelling and water diffusion in hydrophilic samples. This is a perfect tool to follow the evolution of the sample’s shape and the concentration changes due to water uptake. The technique can be easily used to monitor simultaneously different regions of interest in the object and qualitative/quantitative results can be obtained. The application of this method to monitor the water sorption kinetics in a starch-based sample will be presented. The results indicate that water profiles in the sample can be used to estimate, on the basis of Crank equations 3, the water diffusion coefficient along few millimeters