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International Starch Institute
Science Park Aarhus, Denmark
ISI 08-3e Determination of Fibre in Starch as Fibre Number
| 1. Scope | The method is applicable to native potato and cassava starch
|
LT 1965 Rev. LT 30. Jan. 2000 |
| 2. Principle | Starch is hydrolysed and filtered. The discoloration of the filter is
visual judged and compared with an internal standard scale.
|
Corns starches do not filter properly. |
| 3. Apparatus | 3.1 Analytical balance weighing to the nearest 100 mg. | |
| 3.2 Boiling water bath. | Shaking bath convenient | |
| 3.3 Vacuum filter with an active filter area 20 mm in diameter + high flux paper filter. | The diameter of the active filter area is essential. Whatmann No. 1 35 mm diameter Cat. No. 1001 035 |
|
| 4. Reagents | 4.1 Hydrochloric acid 0.1 N | |
| 4.2 Colour plate Carry out the procedure on starch samples containing x ppm insoluble residues on dry matter with x ranging from 100 to 2000. Mark the filter paper with fibre number = x /500 and keep for reference.
|
The procedure is carried out with increasing quantity of same starch. Above 2.5 g the quantity of acid is increased proportionally. | |
| 5. Procedure | 2.5 g sample as is is slurried in a conical flask with 30 ml acid (4.1) | Use 100 ml flask or larger |
Hydrolysis |
Place flask in boiling water bath (3.2) for 20 min | Shake min. until starch is gelatinised |
Filtration |
Filter hot on vacuum filter (3.3). Flush flask and filter with hot water. | Filtration flux must be quick |
| Dry filter at max 105 oC | ||
Judgement |
Compare the visual appearance of the filter with the colour plate and
assign by interpolation the fibre number of best fit.
|
A photometer may be used. |
| 6. Reporting | Report fibre number of sample as is by averaging results of two samples
with one decimal.
|
|
| 7. Notes | Fibre number is useful as internal standard. By reproduction of the
colour plate the initial colour plate should be used for reference securing continuity
rather than from a new independent impurity series. The diameter of the active filter area
is essential.
|
Applying fibre numbers prevent confusion with determination of impurities by weight. |
| 8. Image |
|
Sartorius filter funnel(min 30 ml) with glass vacuum holder for 35 mm filters (20 mm diameter of active filter area), with PTFE-coated steel screen filter support. This support is essential to maitain a high flux. |
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Keywords: laboratory method determination pulp fibre fiber starch
