In order to master the chocolate processes, two parameters must be known and managed very well. These two values are; plastic viscosity and shear stress. Many machine designers, engineers and technologists can make serious mistakes, even today , because they cannot interpret(!) these two values correctly in industrial mass productions.
1- Shear stress or yield value; the minimum pressure that must be overcome before the chocolate flow can begin. In all viscoplastic flows, flow does not start before this limit pressure is exceeded.
2-Plastic viscosity ; the energy required for the chocolate to continue the flow after the flow has started.
Let's give some examples of both;
For Shear Stress-Yield Value (YV) ;The pressure created by the chocolate mass, which is ready for filling in its own depositor plate slot, at the nozzle mouth is approximately as low as 1.2 Pascal . However, in order to make it flow naturally, according to Casson flow model , it must exceed 29.7 Pascal pressure(YV) at 40 C, which can only be achieved with pistons that produce mechanical power.
For Plastic Viscosity;It is a measure of the spread of chocolate filled into moulds, or a measure of the thickness of the chocolate coated on a bakery product , or a factor in calculating the required pump head for the chocolate flowing through the pipelines.
The two main factors in the creation of these two critical process values (PV and YV) in lines with the needs of the production are the formulation and the process.
meaning of formulation; fat concentrations , fat types , emulsifier concentrations , particle size distributions of components
meaning of process; thinning, conching and tempering.