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Brookfield AMETEK

Jelly, Grape

Laboratory Viscometer Application Data Sheet

(TWO METHODS)

USE

Grape Jelly is typically spread onto other foods, such as breads, in making peanut butter and jelly sandwiches, for example, or incorporated into various pastries.

METHOD #1

Test Equipment:

  • Instrument: Standard Viscometer or Rheometer
  • Spring Torque Range: Various, such as RV
  • Spindle: Various T-bars, such as T-E
  • Accessories: Helipath Stand
  • Speed, rpm: Various, such as 5 rpm

* While a particular model/version may be used as an example in this method, any current or past model/version from the same series may also be used. Please consult a sales associate to discuss the most current instrumentation and software available.

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

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 jelly. In our example, we used a Brookfield RVDV-II+Pro Viscometer with Rheocalc v3.1 software for automated instrument control and data acquisition. Representative data from the analyses are shown in Figure 1, below:


Figure 1: Name Brand and Store Brand Grape Jelly at Room Temperature

The name brand product, shown in purple, is somewhat more viscous (between 300,000 and 500,000 cP) than the store brand grape jelly, shown in red (between 200,000 and 400,000 cP). The Helipath data traces progress from "zero" viscosity - before the spindle drills down into the material - to a "plateau" region where the spindle is moving downward in the bulk of the sample. The system then reverses direction and the spindle moves upward continuing to record viscosity data. The measured torque - and calculated viscosity - then drops to "zero" as the spindle rises up and out of the sample. The "plateau" for both product data occurs between approximately 75 and 390 seconds.

The Rheocalc data may be exported to a spreadsheet, and the plateau-region data averaged, to give a QC/QA 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. This last procedure provides a one-point test but as can be seen from the data, the viscosity value can vary significantly.

METHOD #2

Test Equipment:

  • Instrument: YR-1 Yield Stress Rheometer
  • Spring Torque Range: Various, such as HB
  • Spindle: Various vanes, such as V-75; immersed to the primary immersion mark
  • Speed, rpm: 1 rpm

* While a particular model/version may be used as an example in this method, any current or past model/version from the same series may also be used. Please consult a sales associate to discuss the most current instrumentation and software available.

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 jelly. We used the Brookfield HBYR-1 Rheometer, with EZ-Yield™ v1.4 software for automated instrument control and data acquisition. The YR-1 rotational Yield Rheometer performs yield 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 deformation at which the sample structure breaks down - and at which the sample flows. Testing with an HBYR-1, the V-75 vane spindle at 1 rpm produced on-scale results with both products. Representative data from the analyses are shown in Figure 1:


Figure 1: Name Brand and Store Brand Grape Jelly at Room Temperature.

Figure 1 shows that the name brand product has a higher yield stress (130 Pa) than that of the store brand (100 Pa), at room temperature. The name brand grape jelly data are shown in blue, while the store brand data are in purple.

The method using the YR-1 provides a quicker test with data that is easier to interpret compared to the Viscometer with T-bar in Method #1.