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International Starch Institute
Science Park Aarhus, Denmark
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.
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LT 15. Dec. 1964 Rev. LT 21. Nov. 1997 |
| 2. Principle | The starch sample is dried in vacuum at 70 oC
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| 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.
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| 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
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| 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
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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)
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| 7. Notes | Consider the refractive index method
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| 8. Reference | International Standard: ISO 1741 |
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Keywords: laboratory,method,determination,dry matter,substance,starch,vacuum,oven,drying