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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
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|
|Place flask in boiling water bath (3.2) for 20 min||Shake min. until starch is gelatinised|
|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|
|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
|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