ABSTRACT
Not all fluids and semifluids of food importance begin to
flow when a shear stress is applied or have constant visc-
osity with increasing shear stress. For instance, pastes will
not spread easily on a cracker or bread until a certain
additional force is applied in the form of spreading. The
flow behavior of pastes, suspensions, dispersions, and
some syrups fall under the category of non-Newtonian
rheology. Examples are whipped cream, mayonnaise,
ketchup, fruit juice concentrate, vegetable purees, and
corn flour mixed with a little water. Thus, the study of
viscosity and flow behavior of fluids and semifluids may
be extremely complex. They display increasing or decreas-
ing viscosity with increasing shear, a yield stress, time-
dependency, or viscoelastic effects.
