Question

Iodine test is used to confirm the presence of.
A.Fats
B.Proteins
C. Vitamins
D . Carbohydrates

Answer 1

Chemically iodine test is performed to check the presence of starch in the compound. During this reaction, the starch is converted into bluish-black colour by the addition of potassium iodide in the mixture because the polypeptide chains in the starch are broken down into small chains and undergo hydrolysis process.

Complete answer:
Fats: The emulsion test is used for the determination of lipids, in this chemical reaction ethanol and water is used in the mixture. Iodine cannot be used as regent because it is capable of breaking the starch molecules to simple molecules. So, option A is not correct.
Proteins: chemically biuret test is performed to determine the proteins from the compound where the mixture is turned into the violet coloured complex. In the biuret test, the reagent used is sodium hydroxide. So, option B is not correct
Vitamins: In the chemical reaction the Tillman’sHarris test is used to detect the presence of vitamins in the mixture and the reagent used is antimony trichloride. and medically folate test is used to detect the vitamin B12. So, option C is not correct.
Carbohydrates: starch is considered as the main source of carbohydrates. It is a complex carbohydrate hence iodine is used to break the complex molecules into simple molecules of carbohydrates.

Hence, the correct answer is option (D).

Note: By the iodine test the starch can be distinguished from glucose carbohydrate molecules sometimes during this chemical reaction the iodine solution in the compound can turn to yellow or brown colour. This is a simple experiment to test strength. This iodine starch test can be carried out on both liquid and solid food samples.