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International Starch Institute
Science Park Aarhus, Denmark
ISI 16-2e Determination of Alkali Fluidity
| 1. Scope | The method is applicable to thin-boiling starches (acid treated, oxidised) | LT 30.11.1964 Rev. LT 25. Aug. 2000 |
| 2. Principle | Viscosity by the use of a standard funnel
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| 3. Apparatus | 3.1 Analytical balance weighing to the nearest 0.1 mg. 3.2 Funnel approx. Ø 9 cm with short stem and glass tip allowing 100 ml water at 25oC to run out in 70 s +/- 1s, when filled with 110 ml of water. 3.3 Stopwatch 3.4 Water bath with thermostat 3.5 Measuring beaker 100 ml |
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| 4. Reagents | 4.1 Sodium hydroxide 0.25N | |
| 5. Procedure | Weigh sample equivalent to 4.500 g starch dry matter to the nearest mg in
a 250 ml beaker Add 10 ml distilled water and stir with a glass spatula |
See note. |
Gelatinising |
Add 90 ml (4.1) alkaline and stir 3 min. with a glass spatula The starch solution shall be 25 oC +/- 1 oC. Use water bath (3.4) |
Approx. 70 RPM |
Measuring |
Add 110 ml of water at at 25oC. Note the exact time in sec.
for 100 ml of water to run out of the funnel (3.2) preheated to 25oC and
note this water time (T) Transfer gelatinised starch to funnel (3.2) preheated to 25oC and close tip with a finger. Remove finger and start stopwatch. Gelatinised starch is collected in a measuring beaker (3.5). Note volume V in ml after T s. |
Check and note water time before each measurement. Avoid air bobbles |
| 6. Calculation | Calculate alkali fluidity of sample by averaging results of two samples
with no decimal. Alkali fluidity = V |
Largest difference accepted between samples = +/- 4% |
| 7. Note | Results may vary from operator to operator. The variation from sample dry matter is removed by using sample equivalent to 4.5 g dry matter instead of the original 5 g as is. A valve in the funnel outlet for flow adjustment is not recommended. | |
| 8. Reference | Hunt, Henzler and Sowell. Acid hydrolysis of Con Starch. J. Am. Chem. Soc. 41:375-385 (1964) |
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Keywords: laboratory,method,determination,alkali fluidity,viscosity,fluidity,oxidised,acid treated,thinboiling,starch