ISI 04-1e Determination of Dry Matter in Starch Syrup in Vacuum Oven at 70 oC

 

ISI 04-1e Determination of Dry Matter in Starch Syrup in Vacuum Oven at 70 oC

1. Scope The method is applicable to starch hydrolysates, syrups and dextrose mother liquor.

 LT 15. Dec. 1964

Rev. LT 21. Nov. 1997

2. Principle The starch sample is dried in vacuum at 70 o

 

3. Reagent

3.1 Kieselguhr, acid washed and dried.

Wash kieselguhr on a Büchner funnel with water acidified with 1 ml concentrated hydrochloric acid per l until washings turns acid (litmus). Rinse with water until chloride can no longer be detected with silver nitrate, AgNO3. Dry over night at 105 oC. Store in tight container.


4. Apparatus

4.1 Analytical balance weighing to the nearest 1 mg.

4.2 Dish of aluminium or glass with tight-fitting lid

4.3 Electrically heated vacuum oven.

4.4 Desiccator with dry drying agent

4.5 Small stirring rod of glass

4.6 Glass beaker 100 ml

4.7 Weighing pipette, Quickfit

 

5. Procedure

Fill 30 g kieselguhr (3.1) into dish (4.2).

Dry dish, kieselguhr and a stirring rod (4.5) 5 hours in oven (4.3) at 70 oC and max 34 mbar. Alternatively dry at 105 oC over night.

Cool dish in desiccator (4.4) to room temperature and weigh on balance (4.1). Weight = w0 Let cool 1 hour

Weigh 10 g of sample in beaker (4.6) to the nearest 1 mg. Weight = w1. Use weighing pipette (4.7) if possible. Take equivalent to 4 g dry matter

Mix with equal amount of hot water. Stir (4.5) and transfer to dish with kieselguhr. Flush beaker with 3x5 ml hot water. Stir kieselguhr and sample. A weighing pipette make dilution and flushing superfluous

Dry dish and stirring rod 5 hours in vacuum at 70 oC With one dying step only time may be extended

Cool and crush kieselguhr with stirring rod.

Dry again 10 hours in vacuum at 70 oC.

For certain purpose this step may be omitted.

Close lid and cool in desiccator for 1 hour. Weigh immediately after removal from desiccator. Weight=w2

 Possibly re-heat to constant weight

6. Calculation

Dry matter (DM) in percent of sample (average results of two samples to one decimal) =

DM % = 100 x (w2 - w0) / (w1- w0)

7. Notes Consider the refractive index method

  8. Reference International Standard: ISO 1741

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