Determination of amylose
Starch is composed of two components, namely amylose and amylopectin. Amylose is a linear or non-breanched polymer of glucose. The glucose units are joined by a-1-4-glucosidic linkages. Amylose exist in coiled form and each coil contains six glucose residues.
The iodine is adsorbed within the helical coils of amylase to produce a blue colored complex which is measured colorimetrically.
» Distilled water
» 1N NaOH
» 0.1% phenolphthalein
» Iodine Reagent: Dissolve 1g iodine and 10g KI in water and make up to 500mL.
» Standard: Dissolve 100mg amylase in 10mL 1 N NaOH; make up to 100mL with water.
Absorbance corresponds to 2.5ml of test solution = ‘x’ mg amylose
= % amylose
1. The sample suspension may be heated for 10min in a boiling water bath instead of overnight dissolution.
2. The amount of amylopectin is obtained by subtracting the amylose content from that of starch.
1. McCready, R M, Guggolz, J, Siliviera, V and Owens H S (1950) Anal Chem 22 1156.
2. Juliano, B O (1971) Cereal Sci Today 16 334
3. Thayumanavan, B and Sadasivam, S (1984) Plant Foods Hum Nutr 34 253.
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