The flow behavior of chocolates is important both during processing as well as for organoleptic reasons. Another type of vicious behavior exhibited by fluid foods and polymer systems is thixotropy which is again shear-thinning of the material with increasing rates of shear but is also dependent on the duration of shear.īy far the most researched food in terms of viscosity is chocolate. This is referred to as time-independent (steady-state) flow and materials showing this type of behavior are called pseudoplastic. The viscosity of some fluids is dependent on the rate used to shear the material, a high rate of shear making the fluid thinner compared with the fluid that was sheared more slowly. If this is not observed then the liquid is non-Newtonian. An easy way to demonstrate Newtonian behavior is to double the shear stress during a viscosity test and this should result in doubling of the shear rate. However, it must be pointed out that long-chain polymers at low concentrations can also show Newtonian behavior. Newtonian behavior is displayed by simple liquids consisting of small molecules that do not interact or form any connected structure.
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