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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

filterholder.jpg (6607 bytes)

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