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International Starch Institute
Science Park Aarhus, Denmark
ISI 15-1e Determination of Aldehyde Groups in Starch
|1. Scope||The method is applicable to oxidised starch
|2. Principle||Free sulphur dioxide is determined in a mixture of starch and
sodiumbisulphite with and without an alkaline treatment. The difference is the aldehyde
bound sulphur dioxide.
|LT 30 Nov 1964
Rev. LT 03 Sep 1999
|3. Apparatus||3.1 Analytical balance weighing to the nearest 0.1 mg.
3.2 Conical flask 1000 ml
3.3 Burette 25 ml
|4. Reagents||4.1 Sodium bisulphite: 4 g NaHSO3 is dissolved in water. Make
up to 1000 ml with water.
4.2 Sodium thiosulphate 0.1N
4.3 Iodine 0.1N
4.4 Hydrochloric acid 1 N
4.5 Sodium hydroxide 0.1 N
4.6 Sodium thiosulphate 0.02N: 20.0 ml (4.2) Sodium thiosulphate 0.1N diluted to 100 ml with distilled water. Keep one day only.
4.7 Iodine 0.02N: 20.0 ml (4.3) Iodine 0.1N diluted to 100 ml with distilled water. Keep one day only.
|5. Procedure||Weigh 15 g (w) sample to the nearest 0.1 mg in a 1000 ml conical flask|
|Add 550 ml distilled water and gelatinise by heating|
|Cool to room temperature. Add 25 ml (4.1) Sodium bisulphite and make up with distilled water to 600 g. Mix well and let rest for 30 minutes. Label as "Solution A".|
Determination of free SO2
|Add to a 1000 ml conical flask 20.0 ml (4.7) Iodine 0.02N and 15 ml (4.4) Hydrochloric acid 1 N and 100 g "Solution A" and 300 ml distilled water. Titrate excess iodine with (4.6) Sodium thiosulphate 0.02N. Titer = (b) ml|
Determination of free and aldehyde bound SO2
|Add to a 1000 ml conical flask 100 g "Solution A" and 25 ml
(4.5) Sodium hydroxide. Mix and let rest for 15 minutes. Add 20.0 ml (4.7) Iodine 0.02N
and 40 ml (4.4) Hydrochloric acid 1 N and and 300 ml distilled water. Titrate excess
iodine with (4.6) Sodium thiosulphate 0.02N. Titer = (c) ml
|6. Calculation||Calculate aldehyd groups of sample by averaging results of two samples
with two significant digits.
meqv (milli-equivalent) Aldehyde groups per 100 g starch dry matter = (b-c )*Nthio*100 / F; where
w = sample weight, g
|7. Reference||Die Stärke 15, 217 (1963)|
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Keywords: laboratory method determination aldehyde group oxidised oxidized starch