Determination of the Mechanical Properties of Gelatinized Starch Granule from Bulk Suspension Characterization

Gelatinized starch granules are soft and deformable particles that are commonly used in food products as texture modifiers. Modelling the flow behavior of such suspensions during industrial processes requires the knowledge of the mechanical properties of the swollen granules; however, such data is usually lacking because of the difficulties inherent to the determination of mechanical properties of particles that are heterogeneous in terms of size and shape. We investigate here the rheological properties of dense suspensions prepared at different volume fractions and by different means (centrifugation, limited water swelling, osmotic compression) to estimate the mechanical properties of an “averaged” starch granule. Results show that starch granule exhibits a rough surface and behave as frictional particles. We compare the shear modulus value determined assuming either frictionless (previous model) or frictional interactions (as suggested by our results), the latter giving shear modulus lower by about one order of magnitude. This study also allows the first estimate of the starch granule bulk modulus, which value is corresponding to a Poisson ratio of 0.47, close to the maximum value of 0.5. The swollen granule shear modulus is also shown to be temperature independent in the range commonly found in industrial processes (20–90 ∘C). These results pave the way toward multiscale mechanistic modelling of the flow of starch suspensions, to derive macroscopic rheological properties from the description of the microscopic granule properties.