Question

Given below are some food items:

(A) Boiled and mashed potato

(B) Boiled and chewed rice

(C) A slice of bread

(D) Sugar solution

(E) Coconut oil

Which of the above will give blue - black colour when tested with iodine solution?

1. (A) and (C)
2. (B) and (D)
3. (A), (B) and (C)
4. (A), (C) and (E)

Answer 1

Correct Answer - Option 1 : (A) and (C)

Concept:

Test For Starch:

1. Take a small quantity of a food item or a raw ingredient. Put 2-3 drops of dilute iodine solution on it
2. Observe if there is any change in the colour of the food item.
3. A blue-black colour indicates that it contains starch.

Explanation:

• The food items containing starch will give a blue-black colour.
• Starch is a carbohydrate. 
• The carbohydrate-containing food items in the above list are boiled and mashed potato and a slice of bread. 
• The boiled and chewed rice is added to the iodine solution then the colour of iodine will not change because of the digestion of starch into sugars.
• The sugar solution and Coconut oil does not contain starch and hence will not give a blue-black colour. 
• Thereby the correct option is (A) and (C).