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Food Rheology

Food fluids have have a wide range of flow properties. These properties vary by food type and by manufacturer and by batch to batch. Process controls are employed to ensure that a given level of consistency is achieved. In terms of material characterisation, this leads to two major questions :- 1. What is the rheology of this particular food fluid ? and 2. What has changed between batches ?
Low viscosity fluids can generally be adequately characterised by a viscosity measurement. As the fluid becomes more viscous and less Newtonian, then it is more desirable to have shear viscosity curves rather than a viscosity. For spraying the most desirable measurement is the extensional viscosity at the same conditions as the process. We can also model a process and show the relevant changes that can be expected from a change in viscosity.

Going about the job of testing.

Testing always can be classified as either 1. We don't know what it is, and we're finding out about it. or 2. We know what it should be, and we're just checking. The first kind of testing requires some time to check on the fundamentals - is the flow stable? is the temperature optimum ? does it degrade? is it repeatable ? is there significant inhomogeneity ? The second kind of test is generally referred to as QC testing, where we simply repeat what we did before.

Testing for processability should generally be done at rates, pressures and temperatures that resemble those found in the process. For this kind of work, we will generally recommend a capillary rheometer or an extruder. For fundamental chemistry, will generally recommend a rotational rheometer. We can supply results as raw data, or as a model. We can also supply calculated and CFD models of the flow in a process.

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Measured on viscometer
Ideal for looking at simple QC and process control
Basic measurement suited to low viscosity fluids
Automatic process viscometer is useful for process control
Request for Viscosity testing

Shear Viscosity

Measured on lab rotational rheometer
Ideal for chemical modeling
Ideal for viscoelasticity
Request for Shear Viscosity testing

Yield stress

Measured on rotational rheometer
Ideal for looking at stability of suspensions
Request for Yield Stress testing

Shear Viscosity

Measured on lab capillary rheometer
Ideal for processing data
Options are -
Shear Viscosity - Raw data, Power law, Carreau Model
Wall slip
Melt fracture (flow instability)
Request for Shear Viscosity testing

Yield stress

Measured using capillary decay flow
Ideal for shape retention after extrusion
Request for Yield Stress testing

Extensional Viscosity

Measured using contraction flow
Ideal for high rates, low deformation flows
Sensitive measurement for Degradation
Rupture stress
Request for Extensional Viscosity testing

Extensional Viscosity

Measured using pulling flow
Ideal for "sticky" fluids
Request for Extensional Viscosity testing

Analysis of your existing data

We can take your existing data files and :-
Fit data to any standard model
Fit data to shear, extension and slip
.Request for Analysis

Calculation of process effect

We can calculate :-
1. The process pressures that will result from the measurements on your material
2. The process changes that will take place as a result of changes to the rheology of the fluid
Request for Processing Calculations

Rheometer Training

We can train your staff to make a range of measurements and on how to interpret and use the data.
Request for Rheometer Training

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