Thermal stability and composition of the amylose–iodine complex

Amylose–iodine blue complex (absorbance band at 615 nm) was studied at different temperatures to examine the thermal stability and composition of the complex. Our direct experiment with amylose–iodine complex for composition determination suggests that with every 2.75 glucose units of amylose helix there is an iodine unit involved. The average I—I distance in the complex is found to be 3.0 Å, which is in excellent agreement with the value obtained from x‐ray diffraction study of model compounds (3.1 Å). As the temperature increases above 15°C, the observed decrease in concentration of the complex is primarily due to dissociation of iodine from the amylose helix.