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International Starch Institute
Science Park Aarhus, Denmark
ISI 02-1e Determination of Ash in Starch at 900 oC

1. Scope The method is applicable to native and modified (non-oxidised) starch low in ash (<2%).  LT 12 Dec. 1966
Rev. LT 21. Nov. 1997
2. Principle Incineration of starch sample at 900 oC

 

3. Apparatus 3.1 Analytical balance weighing to the nearest 0.1 mg.
3.2 Ashing dish of platinum or quarts
3.3 Electrically heated furnace.
3.4 Desiccator with dry drying agent
3.5 Bunsen burner

 

4. Procedure Careful clean the ashing dish (3.2) and heat it 1/2 hour in furnace (3.3) at 900 oC.

Cool dish in desiccator (3.4) to room temperature and weigh on balance (3.1) to the nearest 0.1 mg. Weight = w0

 Clean always new dish in boiling dilute hydrochloric acid

Cool platinum 15 min, quarts 30 min

Distribute 5 g of sample in a uniform layer in dish. Close lid and weigh on balance (3.1) to the nearest 1 mg. Weight = w1 Take 10 g of maize and tapioca starch

Work quickly

Incinerate the sample on a Bunsen burner (3.5) or equivalent until completely carbonised. Avoid loss of sample by violent fire
Finish the incineration in the furnace (3.3) at 900 oC until residual carbon has disappeared.

Cool in desiccator to room temperature. Weigh immediately after removal from desiccato to the nearest 0.1 mg r. Weight=w2

 

5. Calculation Ash in percent of sample as is (average two results to the second decimal) =

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

 

Correct eventually result to dry matter basis.
6. Notes Use sulphated ash method for hydrolysed, oxidised starch and products high in chloride (>0.2% calculated as NaCl) and high in ash (>2%)  ISI 03-1e
Alternative method: Incinerate at 525 oC to constant weight.

 

Verify
7. Reference International standard: ISO 3593

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