The Iodine Test

What is the iodine test?

Why does iodine turn blue-black with starch?

Try the iodine test at home

You'll need:

• A small bottle of iodine solution (available at most pharmacies)
• A few foods to test — rice, potato, banana, paneer, bread, sugar, milk all work well
• A small plate or saucer for each food
• Cotton swabs or a dropper

Steps:

1. Prepare your samples — Place a small piece of each food on its own plate so the iodine doesn't mix.
2. Add iodine — Drop one or two drops of iodine on each food. Use a fresh swab for each.
3. Wait and observe — Wait 10–20 seconds. Foods that contain starch turn deep blue-black; foods without starch stay brown.
4. Compare results — Note which foods turned dark and which didn't. The dark ones are rich in starch.
5. Clean up — Wash your hands. Iodine can stain skin and clothes. Don't taste the foods after the test.

Frequently asked questions

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