ISI 01-1e Determination of Dry Matter in Starch by Oven Drying at 130 oC
1. Scope The method is
applicable to starch in native or modified form.
LT 15 Dec. 1964
Rev.: LT 21 Nov. 1997
2. Principle The sample is
dried to constant weight.
3. Apparatus 3.2 Dish of
aluminium or glass with tight-fitting lid
3.3 Electrically heated constant-temperature oven.
3.4 Desiccator with dry drying agent
4. Procedure An empty dish
(3.2) is dried 1/2 hour in oven (3.3) at 130 oC. Cool dish
in desiccator (3.4) to room temperature and weigh on balance (3.1) to the
nearest 1 mg. Weight = w0
Let cool 40 min
Distribute 5 g of sample in a uniform layer in dish. Close lid and weigh to
the nearest 1 mg. Weight = w1
Place the open dish with sample in oven preheated to 130 oC.
Dry 90 minutes after oven has once again reached 130 oC.
Close lid and cool in desiccator for 30 to 45 minutes. Weigh immediately
after removal from desiccator to the nearest 1 mg. Weight=w2
Dry starch absorbs atmospheric moisture rapidly. Therefore; close lid fast
and keep desiccator in perfect condition.
Drying too long affects starch
5. Calculation Dry matter (DM)
in percent of sample (average results of two samples to one decimal) =
DM % = 100 x (w2 - w0) / (w1 -
w0)
6. Notes Dry matter
determination by infrared drying to constant weight of sample placed
directly on a laboratory balance gives comparable results. It is a reliable
alternative without the risk of unintended moisture re-absorption associated
with the oven drying method.
Alternative method is drying at 105 oCover night (min. 16
hours).
7. Reference International
Standard: ISO 1666
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