What is the chemical basis of the iodine test?

The iodine test is based on the formation of a complex between iodine and starch. When iodine (I₂) is added to a starch solution, it interacts with the helical structure of amylose, a component of starch, resulting in a blue-black color. This color change indicates the presence of starch, making the iodine test a useful qualitative assay in various applications, such as food testing and laboratory experiments.