Relation between particle properties and rheological characteristics of carrot-derived suspensions

The effect of particle properties on the rheological behaviour of carrot-derived suspensions was investigated systematically. Hereto, a range of relatively monodisperse suspensions, with varying average particle sizes (~73, 176, 262 and 369 µm) and pulp contents (from 30 to 65 wt.%), was prepared by the reconstitution of carrot tissue particles in water. Suspensions with average particle size of ~73 µm consisted of cell fragments, whereas suspensions with larger particle sizes contained mainly cell clusters of which the cell number increased with increasing particle size. The rheological characteristics showed that the carrot-derived suspensions have a non-Newtonian behaviour with a yield stress, depending on particle concentration, size and type. The network structure of all suspensions could be described as a weak gel. Increase in yield stress and storage modulus with particle concentration could be fitted to a power law model. A unique linear relation was found between the yield stress and the plateau modulus, independent of the particle size and type. Particle concentration, size and type appeared to be key structural parameters controlling the rheology of these carrot-derived suspensions. When comparing the rheological behaviour of the reconstituted suspensions with the original carrot purée of similar average diameter and pulp content, the network structure (measured as yield stress or storage modulus) in carrot purée was weaker, which may be attributed to the broader particle size distribution.