Why Can Starch Change The Iodine Solution To Colorless?

What happens if the solution of betadine (iodine) is reacted with starch (rice) and starch (starch)?

      Starch or starch (CAS # 9005-25-8) is a complex carbohydrate that is insoluble in water, in the form of white powder, tasteless and odorless. Starch is the main ingredient produced by plants to store excess glucose (as photosynthesis products) in the long run. Animals and humans also make starch an important energy source. Whereas starch or flour is composed of starch and also a mixture of proteins that are more complex than starch / starch.

Starch is composed of two types of carbohydrates, amylose and amylopectin, in different compositions. Amylose gives hard properties while amylopectin causes stickiness. Amylose gives a deep purple color to the iodine test while amylopectin does not react. Explanations for these symptoms have never been fully explained.

Starch or starch can be separated into two main fractions based on solubility when buried (trituration) with hot water: about 20% starch is amylose (dissolved) and the remaining 80% is amylopectin (insoluble).

1. Amylose can dissolve in water, while amylopectin does not dissolve in water. The starch is a tedricate α-D-glucose polymer that is C-1 and C-4 and unbranched or α (1.4) -D-glucose structure, whereas amylopectin is an α (1.4) -D-glucose chain which branching on C-6 atoms or α (1.6) -D-glucose bonds.

There are 250 units of glucose or more per amylose molecule; the number of units depending on the animal or plant species. (measurement of chain length is confused by the fact that natural amylose is degraded into smaller chains during separation and purification).

2. Amylopectin provides stickiness to rice. The more amylopectin, the more sticky the rice produced by the rice. The more amylose at large, the harder the rice is produced. Rice generally contains amylose more than 20%, while sticky rice has an amylose content of only about 1-2%.

Amylum can be hydrolyzed at high temperatures to produce glucose molecules. In the human body, starch undergoes hydrolysis in the mouth due to the amylase enzyme in the salivary glands and by pancreatic enzymes in the intestine. Heating of starch can turn starch into brown dextrins, for example seen on bread.

For more details, consider the following video!

Now, back to the topic, why did the rice change to a purplish blue or blackish blue color when reacted with iodine solution?

The process of changing the color of rice (starch) into a typical dark blue color due to the bond between the iodine and glucose. Starch solution, there is a glucose unit that forms a helical chain because of the bond with the configuration of each glukos unit. This form causes starch to form complexes with iodine molecules that can enter the spiral, causing dark blue in the complex (Fessenden, 1986).

Why does the iodine solution change color to colorless when dissolved with starch?

Due to the bond between the iodine and glucose where the starch will be hydrolyzed into glucose monomers. The helical chain is formed because of the bond with each of these glucose units along with the release of the iodine which causes the color of the iodine to become colorless (there is a change in color in the solution).

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