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International Starch Institute
Science Park Aarhus, Denmark
ISI 38-3e Determination of Cold Water Solubles by Viscometer
|1. Scope||The method is applicable to commercial starch.
|Jan 1990 rev. Nov. 2002|
|2. Principle||Viscosity of the water phase of a slurry is interpreted as concentration
|cws = cold water solubles|
|3. Apparatus||3.1 Brookfield viscometer RVT
|4. Procedure||Weigh a starch sample w g as is containing 50 g starch dry matter to the nearest g. Add distilled water at ambient temperature to a total of 200 g and stir for 30 minutes.||Equivalent to 21 degree Beaumé starch slurry.|
|The starch is allowed to settle and the viscosity of the supernatant is
measured with the instrument (3.1) and the reading (v) in cps is recorded.
|cps = centipoise
Spindel no. 2 and 60 RPM
|5. Calculation||Report reading as cps without decimals or|
|report with two decimals as cws% as is = 0.0072*v - 0.32
|Check equation and correct if necessary|
|6. Note||The viscosity method is fast and simple. The expression of viscosity as
cws is more expressive, but it is compulsory to attach the method designation to the
Alternative: Filter the sample slurry and dry 50 g of filtrate at 130 oC and calculate the solubles as percentage of sample dry matter.
|By expression as cws the correlation of viscosity to starch solubles
determined by a more direct method should be checked at various levels of cws and found
The method is developed in the potato starch industry. Viscosity determination depends on preparation and sample history. It is therefore advisable to check the equation for use in a particular laboratory and correct if necessary.
|Standarddeviation on the difference should be better than. 0.03% cws|
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Keywords: laboratory method determination cold water soluble starch viscosity