Mixing processes for agricultural and food materials: Part 2, highly viscous liquids and cohesive materials

Abstract

Food and agricultural materials are often Theologically complex; these materials may range from cohesive powders to viscous non-Newtonian fluids to dispersed particles suspended in Newtonian liquids. Several mechanisms are involved in the mixing processes. Mixing processes range from simple diffusion to shear deformation flow and redistribution. In shear flow of materials particle collisions result in rearrangement and thus mixing. Effectiveness of mixing will be determined by which forces are dominant i.e., hydrodynamic versus non-hydrodynamic. The ease of mixing or the tendency toward segregation in particulate materials is determined by the balance of interparticulate forces. Interparticulate binding forces, which are due to moisture, electrostatic bonding and Van der Waals' forces, tend to prevent segregation. Bread making is a good example where great variation in material properties occur during the mixing processes. Part of this change results from energy input by the mixer. Overmixing will result in undesirable property changes and an unacceptable product.