Question

Write a test detecting the presence of starch.

Answer 1

Hint:Starch is the most important complex carbohydrate compound. It is a polysaccharide and glycoside reserve of plants. Starch is used in the detection of redox titrations. It reacts with iodine which turns blue-black in the presence of starch.

Complete answer:The iodine starch test is a chemical reaction that is used to test for the presence of starch or for iodine. Starch is often used in chemistry as an indicator for redox titrations where tri-iodide is present and can be detected using iodine solution. Iodine detects a particular form of starch (helix). It forms a blue-black complex with tri-iodide.
A chemical test for starch is to add an iodine solution and look for a colour change. Take a piece of the food item. Add 2-3 drops of dilute iodine solution on it. If the colour of the food item becomes blue-black, then it indicates the presence of starch in that food and if the colour doesn’t turn into blue-black, then it indicates starch is not present. The combination of starch and iodine is intensely “blue- Black” the interactive between starch and tri-iodide is the basis for iodometry.
Therefore, Blue/ Black colour- Starch is present.
No Blue/ Black colour- Starch is not present.

Note:The Iodine test for starch is mainly performed to test the presence of carbohydrates. The food products which we eat include different types of carbohydrates, among which starch and sugars are the main carbohydrates found in our food products. It is possible to distinguish starch from glucose and other carbohydrates using the iodine solution test.