ISI 19-6e Determination of Viscosity of Starch by Brabender

1. Scope The method is applicable to starch

 

 LT 08.12.1966
Rev. LT 7. Feb. 2000.
2. Principle Viscosity of native and modified starch is measured during controlled heating and cooling

 

 Dynamic viscosity
3. Apparatus 3.1 Brabender viscograph, 700 cmg cartridge. Bowl rotational speed: 75 rpm. Starting temperature: 45 oC. Subsequent rate of temperature increase and decrease: 1½ oC/min. Use standardisation kit for calibrating.
Starting temperature = Start of test.
3.2 Beaker, 1000 ml
3.3 Laboratory scale

 
4. Procedure Weigh starch sample equivalent to x g dry substance (DS), where

x = 20.0 g native potato DS
x = 30.0 g native tapioca starch DS
x = 25.0 g native waxy maize starch
x = 40.0 g native corn starch DS 
x = 40.0 g native wheat starch DS
x = 40.0 g native milo starch DS
x = 40.0 g native rice starch DS
x = 30.0 g native sago starch DS
x = 30.0 g native sweet potato starch DS
x = 25.0 g native waxy sorghum starch DS
x = 25.0 g native waxy rice starch DS
 Native starch concentration:
4% potato
6% tapioca (cassava)
5% waxy corn
8% corn
8% wheat
8% milo
8% rice
6% sago
6% sweet potato
5% waxy sorghum
5% waxy rice

The concentration of a modified starch is adapted to suit the range of the viscograph
Transfer sample to beaker (3.2) and add distilled water to 400 g, and suspend the starch. Additional 100 ml distilled water is used for flushing beaker and added to the slurry.
Pour suspension into viscograph bowl (3.1). Flush beaker (3.2) with 100 ml distilled water. Start viscograph and cooling. Final weight of starch slurry is always 500 g.
R1 step: Heat to 92½ oC with 1½ oC per min. Hold step 1: Keep that temperature 20 min. R2 step: Cool to 50 oC with 1½ oC per min. Hold step 2: Keep that temperature for 20 min.

 

 The R2 step and the Hold Step 2 may be omitted in routine checks.
5. Reporting Note and report without decimals the following torque data from the amylogram inclusive concentration and quantity of starch slurry as well as 700 cmg cartridge or method used Example: Peak visc = 980 BU (15 g DS in 500 g; 700 cmg) or
Peak visc = 980 BU (ISI 19-6)
Gel temp = oC at which viscosity has increased by 20 BU during heating
Peak temp = oC at which viscosity reaches peak value during heating
Peak visc = BU at peak temperature
Visc 93 = BU when temperature reaches 93 oC start holding period
Visc 93/20 = BU after 20 min at 93 oC end holding period
Visc 50 = BU when cooled down to 50 oC
Visc 50/20 = BU after 20 min at 50 oC end of test
Breakdown = Peak visc - Visc 93/20
Setback = Visc 50 - Visc 93/20

BU = Brabender Units
6. Notes See page of comments
7. Reference CRA Standard Analytical Methods B-9
Draft ICC-Standard No. 169

 

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