Viscometer vs. Texture Analyzer

An Interview with Ross Clark

When does a viscometer make sense and when does a texture analyzer make sense? read more

Life Below the Yield

An Interview with Neil Cunningham

It may come as a surprise but most of the liquids in our lives spend most of their lives as solids...read more

AUTOCOATS: WHICH VISCOSITY TEST METHOD SHOULD I USE?

Dr. Lori Boggs Interview

Testing the viscosity of coatings in the automotive world requires a range of devices and instruments...read more

The Ups and Downs of Texture Analysis

Dr. Andrew Rosenthal Interview

Did you ever wonder how food companies evaluate "chewiness" of meat, the "snap" of a biscuit or cracker, the...read more

CUSTOMER CHALLENGE: How can we analyze the mayonnaise texture?

My questions are related to Mayonnaise, that are:

1. How can we analyze the mayonnaise texture?

2. At what temperature we should measure mayonnaise viscosity through offline Brookfield viscometer? (generally we cool mayonnaise from 29 degree Celsius to 25 Degree Celsius)

3. How can we reduce handling error for Viscosity measurement through Brookfield Viscometer?

BROOKFIELD ANSWERS: Thank you for your inquiry.

Viscosity measurement of mayonnaise has traditionally been accomplished with Brookfield T-Bar spindle and Helipath Stand accessory when using Brookfield viscometer with RV Torque Range. New methods allow for use of vane spindle with Brookfield DV3 Rheometer to measure the yield stress in mayonnaise as well as the viscosity.

Texture measurement of mayonnaise is performed with CT3 Texture Analyzer and choice of various fixtures, depending on the physical property of interest. The TA-STF measures spreadability. The TA-DEC measures extrusion. And the TA-MP measures consistency.

Go to the Brookfield website to see images of the above items: www.brookfieldengineering.com.

CUSTOMER CHALLENGE: How to Calculate Shear Rate

I use a standard rotational viscometer with Brookfield spindles. I run my instrument at various rotational speeds, such as 2rpm, 5rpm, 10rpm and 20rpm. How do I know the shear rate?

BROOKFIELD ANSWERS: If the spindle has a disk on the shaft, there is no established formula for converting rotational speed to shear rate... read more

CUSTOMER CHALLENGE: 3 Part Yield Stress Challenge

Part 1: How can I measure yield stress with my rotational viscometer?

BROOKFIELD ANSWERS: Use the Small Sample Adapter accessory with the viccometer. Run a viscosity test at several increasing speeds such as 5, 10, 20 and 50rpm. Plot the shear stress values at each speed vs. the equivalent shear rate values. Use a best fit line through the data points and determine where the line intercepts the y-axis. This point of intersection with the y-axis is the yield stress value. This method is an approximation because it uses viscosity data for the fluid after it is in motion.

Part 2: Is there a simpler way to do this type of test for yield stress automatically?

BROOKFIELD ANSWERS: Use a PC with Rheocalc software to run the test, capture the data, and then use a math model such as Casson or Bingham which will calculate the yield stress value automatically.

Part 3: Is there an instrument that can measure yield stress directly?

BROOKFIELD ANSWERS: A controlled stress rheometer can perform the measurement of yield stress directly.