Hinglish

Testing Components of Food

Class 6 Science · Chapter 3: Mindful Eating: A Path to a Healthy Body · NCERT Curiosity section 3.3

Learn

How do we know which foods have starch, fat or protein? With simple tests! Anjali's class sets up a testing table with small samples of foods, droppers and white paper. (Chemicals are handled only with the teacher's help.)

Starch test: put 2–3 drops of dilute iodine solution on the food. If it turns blue-black, the food has starch. A potato slice turns blue-black; a drop of sugar water stays brown.

Fat test: rub the food on a piece of paper and let it dry. A see-through, oily patch that stays after drying means fat. Water also makes a wet patch, but it dries away.

Protein test: a food paste is mixed with water, then a few drops of copper sulphate solution and caustic soda solution are added by the teacher. A violet colour shows protein: egg white and dal paste turn violet.

Explore: run the tests yourself.

  1. Test each food with iodine, then tick the ones with starch.
  2. Now do the paper test and tick the foods with fat.

Remember

  • Starch: iodine turns blue-black. Fat: a see-through oily patch on paper. Protein: violet colour.
  • Always do tests with care, and handle chemicals only with a teacher.

Quick check

Iodine solution on a slice of bread turns blue-black. What does this show?

  1. Bread contains starch
  2. Bread contains fat
  3. Bread contains vitamin C
  4. Bread has no nutrients
Answer

Bread contains starch. Blue-black with iodine is the sign of starch.

Think about it

Rohan says, "Rice has no protein because the iodine test turned blue-black." What is wrong with his reasoning?

One answer

The iodine test only tells us about starch. To know about protein he must do the protein test. A food can contain several components at once.

Practice

Practise with fresh questions at three levels (easy, medium, hard), some answered hands-on, with hints and worked answers. Get 4 of your last 5 right to finish the topic.