Laboratory Tests for Nutrients

Testing Food Components

We can scientifically verify which nutrients are present in food using simple chemical tests.

1. Test for Starch (Carbohydrate)

Starch turns blue-black when it reacts with Iodine.

• Materials: Dilute Iodine solution, dropper, food sample (e.g., potato).
• Procedure:
  1. Take a small quantity of the food item.
  2. Add 2-3 drops of dilute Iodine solution to it.
  3. Observe the colour change.
• Observation: If the food turns Blue-Black, it contains Starch.

2. Test for Fats

Fats leave an oily stain on paper.

• Materials: Paper, food sample (e.g., peanut).
• Procedure:
  1. Wrap the food item in a piece of paper and crush it (don’t tear the paper).
  2. Straighten the paper and hold it against the light.
• Observation: An oily transparent patch indicates the presence of Fat. (If the paper is just wet from water, let it dry; water evaporates, oil does not).

3. Test for Proteins

Proteins react with Copper Sulphate and Caustic Soda to turn Violet.

• Materials: Copper Sulphate solution, Caustic Soda solution, test tube, dropper, food paste (e.g., mashed dal).
• Procedure:
  1. Make a paste of the food item and put it in a test tube with some water. Shake well.
  2. Add 2 drops of Copper Sulphate solution.
  3. Add 10 drops of Caustic Soda solution.
  4. Shake well and let it stand.
• Observation: A Violet colour indicates the presence of Protein.

Logic Flow for Testing