Newtonian

Refers to true viscous flow, where the shear rate is directly proportional to shear stress applied. Most foods are non-Newtonian and deviate strongly from Newtonian behaviour.

Newtonian fluids has its shear rate directly proportional to shear stress begins at origin. Therefore slope of the line (viscosity) at any shear rate is the same.But the slopes of the lines differ at points along a plastic curve. This would mean change in viscosity.

Plastic flow
Occurs when minimum shear stress exceeded before flow begins. This is very common in foods. For each food that displays this property, there is a point at which flow starts the plastic yield stress. (does not start from 0 and must start above 0 in order for shearing to occur)

Pseudoplastic
Starts at origin and is Newtonian for a while but eventually flattens. (Curves then reaches back to the same gradient as the beginning)

Dilatant
Characterized by escalating viscosity with shear rate. Only occurs in high concentration suspensions, such as raw starch and chocolate syrups which contain insoluble rigid particles. For dilatancy to occur, the particles have to exist in close packed form. When this is disturbed by shear, viscosity increases.

Just some basic terminology, if you can imagine molecules in parrallel and molecules which are juttered out. Parrallel can be like pringles and molecules with ends or kinks could be a generic brand of chip. Being parallel enables shear rate to reach a point where shearing does not effect it as the force is just allowed through due to the parallel arrangement of molecules whilst molecule with kinks will create friction(resistance).Quicky summery on viscosity, may update it. (Most likely not)