Student’s Name:

Determination of the rheological characteristic of mayonnaise

BAEN /CHEN-422-622 page 1 of 6

UNIT OPERATION IN FOOD PROCESSING

Department of Biological and Agricultural Engineering

Texas A&M University

Lab # - Rheology

The product The rheometer The spindles

Model

Number

Torque Range

[dynes-cm]

Shear Stress Range

[Pa]

LV 673.7 10-90

RV 7,187 5-100

HA 14,374 1-200

HB 57,493 4-800

1) Describe the system used to measure the rheological properties of mayonnaise

Rhreometer model:

Spindle type and number:

2) Define if the method is empirical or fundamental, why?

Fundamental: concentric cylinder - Searle or Couette flow - measures shear stress and shear rate

Empirical: any spindle (disk) in a beaker - measures torque and rpm

3) Is mayonnaise thixotropic? Explain your answer.

Thixotropy - is the property of some non-newtonian fluids to show a time-dependent change in viscosity; the longer the fluid undergoes shear, the lower its viscosity.

(a) (b)

4) Calculate the shear stress and shear rate data and determine the rheological properties of this product using only the upper curve results.

BAEN /CHEN-422-622 page 2 of 6

UNIT OPERATION IN FOOD PROCESSING

Department of Biological and Agricultural Engineering

Texas A&M University

Lab 1 - Rheology

Brookfield spindle kσ [Pa]

1 0.035

2 0.119

3 0.279

4 0.539

5 1.05

6 2.35

7 8.40

Brookfield Model M [dyne.cm] C

1/2 RV 3,584 0.5

RV 7,187 1.0

HA 14,374 2.0

HB 57,496 8.0

Determination of the rheological characteristic of soybean oil

Table 1 : Information on the sensor available for couette flow configuration

BAEN /CHEN-422-622 page 3 of 6

UNIT OPERATION IN FOOD PROCESSING

Department of Biological and Agricultural Engineering

Texas A&M University

Lab 1 - Rheology

The product

The sensor

SC4-18 SC4-21 SC4-28

Rotor (BOB)diameter (cm)equivalent length (cm)

1.73.3

1.63.3

0.83.3

Stator (CUP)diameter (cm)height (cm)

2.056.3

2.056.3

2.056.3

HBDV-III is equipped with a head which gives a torque reading of

574.96 dyn m/scale grad. Full scale is 0 to 57,496 dyn- cm for 0 to 100

scale range.

1) Describe the system used to measure the rheological properties of soybean oil

2) Define if the method is empirical or fundamental, why?

3) Is soybean oil Newtonian or non-Newtonian, Thixotropic? Explain

4) Calculate the Shear stress and shear rate for a specific torque value

Method σ [Pa]

γ[1/s]

Newtonian approximation

Viscometer value

Torque ___________ [Nm] angular velocity ___________ [rad/s]

Cup dimensions: d = 27.62 [mm]

BOB dimensions: h = 92.39 [mm] d = 25.15 [mm]

α = Rc/Rb = __________

Discuss your results:

BAEN /CHEN-422-622 page 4 of 6

UNIT OPERATION IN FOOD PROCESSING

Department of Biological and Agricultural Engineering

Texas A&M University

Lab 1 - Rheology

Shear stress calculation - concentric cylinder

Shear rate calculation - approximations

Newtonian Power-Law

BAEN /CHEN-422-622 page 5 of 6

UNIT OPERATION IN FOOD PROCESSING

Department of Biological and Agricultural Engineering

Texas A&M University

Lab 1 - Rheology

M = torque

h = bob hight

Rb = bob radius

Rc = cup radius

Ω = angular velocity = 2πN/60

Determination of the yield stress of ketchup

1) Describe the system used to measure the yield of ketchup

2) Describe the procedure to measure the yield stress

BAEN /CHEN-422-622 page 6 of 6

UNIT OPERATION IN FOOD PROCESSING

Department of Biological and Agricultural Engineering

Texas A&M University

Lab 1 - Rheology

The product The rheometer

The vanes

The results