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# Food Microbiology

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1.Herschley-Bulkley Model

Please describe in detail this model indicating the meaning of each parameter and their range.
Please list and describe alternative THREE PARAMETER Models.

2.Creep Test

Please describe in detail this test and explain why is so useful in characterizing viscoelasticity.

3.Relaxation test

Please describe in detail this test and explain why is so useful in characterizing viscoelasticity

4.Capillary Tube

Provide information related to:
How does this instrument work?
Fundamental equations
Limitations

5.Rotational Rheometers

Provide information related to:
Principle of operation
Geometries associated with the instrument
Fundamental equations
Limitations
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Please answer all the questions with the references.

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https://brainmass.com/biology/microbiology/food-microbiology-104355

#### Solution Preview

See the attached file.
1. Hershel-Buckley
The Hershel-Buckley model describes the behavior of a fluid that behaves in an unusual manner (rheology; see http://www.tipmagazine.com/tip/INPHFA/vol-10/iss-2/p29.html). The BH equation is given as (also given in attachment 0gl99112):

shearing stress=yield stress + consistency (shear rate) ^ power law exponent

The three parameters of HB are yield stress, consistency and shear rate. BH model requires a certain amount of stress (a threshold) to initiate flow but require less stress as sheer increases. Yield stress is the amount of force required to cause deformation. Consistensy describes the ability to flow. Its range is dependent on temperature and solute content. Sheer stress is defined as the force divided by the area parallel to the force. From my understanding the ranges of these parameters depends on the material and experiemtnal design. I've found a few studies for you to review for more information (the last link is a good overview):