Rheology

Question 1

Food texture testing spectrum scale

Answer 1

Non-destructive
- Creep compliance - Oscillatory testing

Combination
- Stretching - Bending

Destructive
- Cutting - Breaking

Question 2

Thixotropy

Answer 2

Viscosity reduced by shaking, stirring or mechanical agitation

Shear thinning, e.g. ketchup

Question 3

Rheopecty

Answer 3

Viscosity increases under shear in a time dependent manner

Question 4

Dilatant fluid

Answer 4

Shear thickening, e.g. silly putty, custard, quicksand

Question 5

Mechanical models of a viscoelastic system (3)

Answer 5

Elastic/spring
which the spring components can stretch and recover elastically

Viscous/dashpot
The dashpots expand and recover only at the damped rate

2 different type of Viscoelastic systems

Question 6

For the Mechanical models:

The elastic component is known as ?

The dashpot is the what component ?

Answer 6

The elastic component is known as the spring’s compliance and is a J value

The dashpot is the viscous component (Greek letter eta) see slide 8