Applies to modified starch, both granular and soluble in cold water. The methods specified enable to measure total and free acetyl contents; bound acetyl content is calculated as the difference of the two values. Total content is determined by heating the sample with dilute hydrochloric acid and converting the acetate with adenosine-5-triphosphate (ATP) and coenzyme A (CoA) to acetyl-CoA. The methods are suitable for determining acetyl contents up to 2 % (m/m).
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Sisällysluettelo
Foreword
1 Scope
2 Normative references
3 Principle
4 Reagents and materials
4.4 ATP-CoA-NAD solution.
4.5 MDH-CS suspension.
4.6 ACS solution.
5 Apparatus
6 Preparation of the sample
7 Procedure
7.1 Hydrolysis of acetyl groups
7.2 Free acetate
7.3 Check test
7.4 Enzymatic determination of acetic acid
8 Expression of results
8.1 Absorbance difference
8.2 Total acetyl content
8.3 Free acetyl content
8.4 Bound acetyl content
9 Precision
9.1 Repeatability
9.2 Reproducibility
10 Test report
Annex A Derivation of equation for calculation of acetyl content (informative)
Annex В Statistical results of the interlaboratory test (informative)