Question

Write the procedure you followed in the laboratory to test the presence of carbohydrates in food items.​

Answer 1

Answer

The main carbohydrates found in our food are in the form of starch and sugars.

...

Test for Starch

Take small quantity of the food items to be tested.

Put 2-3 drops of iodine solution on it.

Observe the colour of the food item.

Blue-black colour indicates the presence of starch in the tested food item.

Answer 2

Carbohydrate is constructed from carbon and hydrogen. Carbohydrates are mixtures of the chemical elements carbon and hydrogen with oxygen.

We can use the following test to identify the presence of carbohydrate -

• (a) Molisch’s test - This test is provided by almost all carbohydrates. In this test, concentrated sulfuric acid modifies the provided carbohydrate into its derivatives, which respond with α-naphthol to construct a purple-coloured product.
• (b) Fehling’s Test - This experiment is done for reducing sugars. To the aqueous solution of carbohydrates, Fehling's solution is put in and warmed up in the water. The construction of red deposition demonstrates the existence of reducing sugars. The copper ions that exist in Fehling's solution in the +3 state are reduced to the +2 oxidation state and in an alkaline medium, it is poured as red cuprous oxide.
• (C) Tollen’s Test - This test is performed for also reducing sugars. Carbohydrates react with Tollens reagent and construct a silver mirror on the internal sides of the test tube. This demonstrates the existence of reducing sugars, Here silver ions are reduced to metallic silver.

#SPJ2