ISI 07-2e Determination of Starch in Pulp by Ewers

ISI 07-2e Determination of Starch in Pulp by Ewers

1. ScopeThe method is applicable to potato and cassava pulp.LT 22 Feb. 1966
Rev.  LT 11. Dec. 1997
2. PrincipleGranular starch is hydrolysed and determined by Ewers polarimetric method.By-product from starch extraction
3. Apparatus3.1 Analytical balance weighing to the nearest 1 mg.
3.2 Polarimeter with 2 dm tube
3.3 Shaking boiling water bath.
3.4 Volumetric flask, 100 ml with wide neck
3.5 Büchner funnel

 

4. Reagents4.1 Dilute hydrochloric acid 0.12 N
4.2 Lead solution, saturated
Dissolve 70 g Pb(CH3COO)2, 3 H2O in 100 ml hot distilled water.

 

5. ProcedureWeigh 10.00 g (w1) wet pulp sample.

Preparation

Slurry sample in 500 ml water and filter through Büchner funnel (3.5) and paper. Wash with 1 l water.Do not let pulp dry out during washing

Hydrolysis

Transfer washed sample to volumetric flask (3.4) and flush down sample with 60 ml diluted hydrochloric acid (4.1).
Place volumetric flask in boiling water bath (3.3) for 15.0 minShake min. 3 min initially

 Clarification

Cool flask in cold water to 20 oC. Add 4 ml lead solution (4.2). Fill to mark with water. Shake and leave to stand for 45 min.Cool rapidly
Filter through funnel and paper.Repeat with more lead solution if not clear

Measurement

Measure optical rotation (a1) of the filtrate with the polarimeter (3.2)

 

6. CalculationStarch in percent of sample (average results of two samples without decimals) =

Starch % = 1000000 *a 1 / (a D*2*w1)

Value of a D at 589.3 nm for starch from:
potato = +185.7
cassava = +184.0
Correct eventually to starch on pulp dry matter (dry 5 g sample at 130 oC for two hours).

 

Juice in pulp affects value on dry matter
7. NotesProper clarification is essential. Alternative: Clarify with Carrez solutions.Residual juice dims polarimeter readings
"Bound" starch may be determined by exchanging the Büchner funnel with a screen during preparation. This procedure, however, does not properly distinguish between starch in intact cells and starch otherwise retained.120 micron openings
An informative figure is the ration of starch to fibre. The fibre fraction is found by solving the equation: "Dry matter = starch + solubles + fibre". The solubles is process dependent and can be found by drying an aliquot of washing water obtained in "preparation".

 

8. ReferenceInternational Standard: ISO 10520

Comments

Post a Comment

Popular posts from this blog

ISI 14-2e Determination of Acetyl Content

  ISI 14-2e Determination of Acetyl Content 1. Scope The method is applicable to acetylated starch   KM Rev. LT 14 Sep 1999 2. Principle Bound acetyl reacts with strong alkali and excess alkali is titrated   3. Apparatus 3.1 Burette 3.2 Conical flask, Erlenmeyer 250 ml with stopper   4. Reagents 4.1 Sodium hydroxide 0.1 N 4.2 Sodium hydroxide 0.45 N 4.3 Hydrochloric acid 0.2 N 4.4 Phenolphthalein: 1 g in 1 l ethanol 90%   5. Procedure Weigh 5 g of sample to the nearest mg. Transfer to conical flask (3.2) and disperse in 50 ml distilled water. Add a few drops of indicator (4.4) and titrate with (4.1) to permanent pink colour. Bound acetyl reaction Add 25.0 ml of NaOH 0.45 N (4.2). Stopper and shake vigorously for ½ hour Use mechanical shaker Titration  Flush stopper and neck of flask with a little distilled water and titrate excess alkali with 0.2N HCL to disappearance of pink colour. Blank 25.0 ml 0.45N NaOH (4.2) is titrated as a blank   6. Calculatio...
Read more

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

Return 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  o C. Subsequent rate of temperature increase and decrease: 1½  o C/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 eq...
Read more

ISI 17-1e Determination of Viscosity of Starch by Brookfield

Image
ISI 17-1e Determination of Viscosity of Starch by Brookfield 1. Scope The method is applicable to native and modified starch - preferably starch for sizing of paper and textiles. LT 7. Oct. 2002. 2. Principle Viscosity of starch size prepared by indirect heating is measured as torque on a rotating spindle at constant speed and temperature 3. Apparatus 3.1 Brookfield Viscometer  RVDV-E (RV range) Alternative: LV range 3.2 Beaker, 1000 ml 3.3 Laboratory scale 3.4 Agitator with paddle stirrer IKA EUROSTAR digital + IKA paddle stirrer R1373 3.4 Boiling water bath and lid with slit for paddle stirrer Bath large enough for lid to cover bath and beaker 4. Procedure Weigh starch sample equivalent to 50 g (w) dry substance (DS) in a beaker (3.2) and add distilled water bringing total weight of starch and water to 500 g.  Put stirrer (3.4) in the beaker. Weigh the total weight of beaker, stirrer, starch and water (W g) Transfer beaker (3.2) to a boiling water bath. Attach stirrer to ag...
Read more