ISI 23-1e Determination of Alkali Lability
ISI 23-1e Determination of Alkali Lability 1. Scope The method is applicable to starch, dextrin, acid and enzyme modified starch LT 17 Dec.1964 Rev. LT 30 Aug 1999 2. Principle Acid is released by reorganising aldehyde end-groups in an alkaline environment. Ester groups such as acetate and adipate are hydrolysed by alkali. The acid is titrated as a comparative measurement of aldehyde-groups and thereby also of starch molecule length. 3. Apparatus 3.1 Analytical balance weighing to the nearest 0.1 mg. 3.2 Stopwatch 3.3 Water bath 3.4 Beaker 400 ml 3.5 Conical flask 250 ml and rubber stopper with one hole fitted with a glass tube closed in one end by a rubber tubing. The free end of the rubber tubing is closed and a slit is cut in the tubing. The slit is functioning as a valve for the whole assembly. Vigorously boiling 3.6 pH-metre or titrator 4. Reagents 4.1 Sodium hydroxide 0.4N, carbonate free. 4.2 Hydrochloric acid 0.2N 4.3 Sodium hydroxide 0.1N 4.4 Hydrochloric acid 0.1N 5.