ISI 17-1e Determination of Viscosity of Starch by Brookfield

ISI 17-1e Determination of Viscosity of Starch by Brookfield




1. ScopeThe method is applicable to native and modified starch - preferably starch for sizing of paper and textiles.
LT 7. Oct. 2002.
2. PrincipleViscosity of starch size prepared by indirect heating is measured as torque on a rotating spindle at constant speed and temperature
3. Apparatus3.1 Brookfield Viscometer  RVDV-E (RV range)Alternative: LV range
3.2 Beaker, 1000 ml
3.3 Laboratory scale
3.4 Agitator with paddle stirrerIKA EUROSTAR digital +
IKA paddle stirrer R1373
3.4 Boiling water bath and lid with slit for paddle stirrerBath large enough for lid to cover bath and beaker
4. ProcedureWeigh starch sample equivalent to 50 g (w) dry substance (DS) in a beaker (3.2) and add distilled water bringing total weight of starch and water to 500 g. 



Put stirrer (3.4) in the beaker. Weigh the total weight of beaker, stirrer, starch and water (W g)
Transfer beaker (3.2) to a boiling water bath. Attach stirrer to agitator and stir with a constant speed of 250 Rotations Per Minute (RPM)RPM must be reproducible.
Stop stirring after 15 minutes, but continue heating for additional 15 minutes. Remove stirrer from agitator, but keep stirrer in beaker. Lift beaker with stirrer out of water bath. Replace evaporated water by weighing and adding water up to gross weight W g.
Cool in running water to 50 oC  while stirring.Alternative: 50 oC
Measure the viscosity in centipoises (cp) with viscometer (3.1) at 50 oC at 100 RPM with spindle No. 2Alternative: LVDV-E (LV range) at 60 RPM.
5. ReportingReport viscosity in cp without decimals. Do also report method, concentration of starch dry matter,  measuring temperature, instrument model, spindle number and spindle RPM.Results are method sensitive
Reporting viscosity without details this method assume a cooked starch slurry with 10% starch dry substance measured at 50 oC with Brookfield  RVDV-E (DV range) at 100 RPM with spindle No. 2
For certain applications it is custom to measure viscosity at 30 oC and temperature must be reported. 
Certain starches may require a different concentration due to their viscosity and the actual concentration of the starch slurry must be reported.
If a Brookfield Viscometer Type  LVDV-E (LV range) is available, this instrument may be used with 60 RPM of spindle. The instrument type, spindle number and RPM must be reported.Various instruments, RPM and spindel give different results.
6. NotesThe sample beaker must be surrounded by hot saturated air during boiling, hence the lid covering the bath and the sample beaker completely - just with an opening slit for the stirrer.

Boiling, cooling and stirring procedures affects viscosity. It is important to reproduce these preparative procedures as well as measurements exactly in order to compare samples.

7. Images
IKA EUROSTAR digital +
IKA paddle stirrer R1373

Brookfield RVDV-E

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