Brookfield Engineering

Ketchup

Laboratory Viscometer Application Data Sheet

(TWO METHODS)

USE

Ketchup is a condiment or dressing. It is typically poured, "squirted" or spread onto other foods, such as hamburgers, frankfurters [or "hot dogs"], other sliced meats or poultry, French fries, and in making sandwiches, for example.

MEHTHOD #1

Test Equipment:

  • Instrument: DV-I Prime or DV2T Viscometer
  • Spring Torque Range: Various, such as RV
  • Spindle: Various T-bars, such as T-B or T-C
  • Accessory: Helipath Stand
  • Speed, rpm: Various, such as 6 rpm

The test may be run at room temperature, or at refrigeration temperatures. The DV-I Prime provides continuous measurement of both torque and viscosity. The DV2T also provides continuous temperature measurement.

The Helipath Stand may be used with various Brookfield Viscometers or Rheometers. The choice of Spring Torque Range, spindle and speed may vary widely, depending upon the ketchup. In our example, we used a Brookfield RVDV-II+PRO, with Rheocalc v3.1 software for automated instrument control and data acquisition. Representative data from the analyses are shown in Figure 1:


Figure 1: Viscosity Data for Name Brand and Store Brand Ketchup at Room Temperature

The name brand product, shown in purple, is slightly more viscous than the store brand ketchup, shown in blue. The Helipath data starts at "zero" viscosity - before the spindle drills down into the material - and climbs to a "plateau" region where the spindle is in the bulk of the sample. The system then reverses direction, and the measured torque and calculated viscosity drops to "zero" as the spindle rises up and out of the sample. The "plateau" region for both products occurs between approximately 30 and 380 seconds.

The Rheocalc data may be exported to a spreadsheet, and the plateau-region data averaged, to give a QC number for viscosity. On the other hand, the Data Averaging feature available in the Rheocalc Wizard may also be used to output averaged data values. Another choice may be to simply have the system "drill" down into the sample for a specified amount of time, say 100 or 120 seconds, and then have the operator record the viscosity value at that time.

MEHTHOD #2

Test Equipment:

  • Instrument: YR-1 Yield Stress Rheometer
  • Spring Torque Range: Various, such as RV
  • Spindle: Various vane spindles, such as V-73; immersed to the primary immersion mark
  • Speed, rpm: 1 rpm

The test may be run at room temperature, or at refrigeration temperatures.

The choice of Spring Torque Range, spindle and speed may vary widely, depending upon the "thickness" of the ketchup. We used the Brookfield RVYR-1 Rheometer with EZ-YieldTM v1.4 software for automated instrument control and data acquisition. The YR-1 performs yield stress tests. The yield stress may be defined as the stress that must be applied to make a solid material flow like a liquid. The corresponding apparent yield strain is the amount of deformation or movement that occurs before the sample structure breaks down and starts to flow.

Representative data from tests run on the same two ketchups in Method #1 are shown in Figure 1:


Figure 1: Yield Stress Data for Name Brand and Store Brand Ketchups at Room Temperature

Figure 1 shows that the name brand product has a higher yield stress than that of the store brand at room temperature, 78 Pa vs. 68 Pa. The slope of the data line for both products leading up to the yield stress is similar, which implies that the "stiffness" of both products may be the same. The name brand ketchup data are shown in blue, while the store brand data are in green. Testing with an RVYR-1, the V-73 vane spindle at 1 rpm produced on-scale results with both products. If the test were run at a slower speed, the curves would shift to the right and the slope of the data line would be less. If the tests were run at a higher speed, the curves would shift left with a steeper slope.