Dynamic rheological properties of plant cell-wall particle dispersions

The theological behaviour of plant cell-wall particle dispersions was investigated using dynamic oscillatory measurements. Two starting plant materials, broccoli stem and carrot were used and two types of particles were obtained by mechanically shearing blanched (80 degrees C, 10 min) or cooked (100 degrees C, 15 min) plant tissues. Blanching resulted in cell-wall particles made up of a collection of clusters of cells with an average particles size of similar to 200 mu m, while cooking generated nearly all single-cell particles with an average particle size of similar to 80 mu m. The rheological measurements showed that in the range of weight concentrations considered (similar to 0.5% to similar to 8%) the dispersions behaved as elastic materials with the elastic modulus G' higher than G '' within the frequency range (0.01-10 Hz). This study shows that the behaviour of the complex modulus G* as a function of the effective volume fraction phi can be modelled using different theoretical equations. To do so, it is assumed that below a critical volume fraction phi(c) a network of plant cell-wall particles was formed and G* as a function of phi obeys a power-law relationship. However above phi(c), where the particles were highly packed. G* could be modelled using theoretical equations developed for concentrated emulsions and elastic particle dispersions. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.