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Use tea to detect iron in food

You will need:

  • 5 tea bags
  • 1 litre of hot water
  • 100g each of different food samples
  • Coffee filters and disposable cups
  • 1 Blender


1. Place the tea bags in the hot water and allow the tea to brew over 10 minutes. You want it strong!

2. Blend the food samples with water.

3. Filter the puree using the coffee filters. Collect the filtrate (the liquid) in the disposable cups.

4. Slowly add the tea brew to the filtrate in the cups whilst stirring. You may see a black solid form
tea bag

Why Does This Happen?

Tea contains tannins, chemical compounds found in plants. Tannins are used by the leather making industry to tan leather, as well as to influence the taste of wine.

Tannins also bind to iron in a process called chelation. If there was iron present in your food you would have found a tiny amount of a black solid (known as a precipitate). You need iron to make red blood cells. If you drink too much tea you may stop iron in your food being absorbed by your body!

Drinking tea is good for you, but try to avoid drinking tea when eating if you know you're low in iron.

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