Non-invasive Determination of Functional and Structural Properties of Materials

Magnetic Resonance Imaging (MRI) is a powerful non-invasive technique with a plethora of applications ranging from the life sciences to solid state chemistry. Applications for the determination of viscoelastic properties and structural information of food products will be discussed. As viscoelastic properties of soft matter can vary by more than two orders of magnitude, material stiffness could provide good image contrast. MR Elastography (MRE) maps spatial displacement patterns corresponding to harmonic shear waves initiated by the mechanical oscillations of an attached actuator. It will be shown how MRE can be used to non-invasively study material properties of food products. Furthermore, conventional MRI can also be used to study drying processes in food and obtain structural information. The water distribution in many bulk food products, e.g. grains, is non-uniform, prior to and during drying. Calculations modeling the drying characteristics of these materials are often hampered by oversimplifications. MRI can be used to map the inhomogeneous water distribution and the spatially resolved diffusion coefficients of these foods as a function of time. The diffusion weighting-time dependence of the diffusion constant provides valuable information on the structural details of the materials. The resulting data can be used as input for more sophisticated model calculations in 2 and 3 dimensions. Applications of MRE and conventional MRI to food products will be presented.