Probing maltodextrins surface properties by atomic force microscopy: Interplay of glass transition and reconstitution properties

Reconstitution kinetics of three maltodextrins powders with different dextrose-equivalent (DE) values (low, intermediate, high DE) were evaluated under the glassy and rubbery states. Reconstitution times were found mostly shear rate of agitation in water and DE dependent in the glassy state, with shorter reconstitution times for high shear rates and DE. For powders under the rubbery state, reconstitution times were less shear rate dependent, especially for high DE values. To have a better understanding of powder surface features that can impact reconstitution properties, single particles surface topographies and nanomechanical properties were probed by Atomic Force Microscopy (AFM). It was shown that surface roughness was higher for high DE maltodextrins under the glassy state, whereas a surface smoothing and slight hollows formation was observed for all powders under the rubbery state. Also, a significant reduction and uniformity of Young modulus at the particle surface were observed under the rubbery state. Finally, surface modification at microscale (smoothing and softening) was linked to powder behavior evolution at macroscale (relative shear rate independence during reconstitution) when the powder crosses the glass transition.