Brookfield Engineering

Jams

Laboratory Viscometer Application Data Sheet

USE

Jams are spread onto breads, used as fillings in pies and pastries or as decorative coatings on confectionary items.

ISSUE

Traditional viscosity testing with a viscometer and accessory, such as a t-bar spindle, can be difficult as jams often have solid particles (fruit) which can cause large variations in centipoise (cP) values. The R/S+SST and a yield test easily produces two numbers, yield stress value and modulus (slope of line leading up to yield stress), which are used to evaluate the fluids in less than 30 seconds.

Test Equipment:

  • Instrument: R/S+SST Rheometer (Soft Solids Tester)
  • Geometry: V80-40, V40-20 Vane Spindles
  • Software: RHEO2000

TEST METHOD

Controlled by Shear Rate (CSR)

PROGRAM

  • One step,
  • Start RPM = 0.5
  • End RPM = 0.5
  • Time = 20 seconds
  • Plot = Shear Stress on Y1, Time on X, no Y2

The graph shows data for two different types of jams which are easily distinguished from each other. The fig jam has a yield stress just below 1000Pa while the blueberry jam yields at a much lower value around 300 Pa. The vane spindle geometry easily accommodates jams of varying consistency and produces a repeatable curve that allows for a quick pass/fail test.