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Minor Versionm

by Procheta Mallik


Using sodium hydroxide and copper sulphate, one can create a solution that is a good indicator to detect the presence of protein in a food substance. Here, we perform the test on few daily life food items.

Video Overview

    • Sodium Hydroxide (NaOH) is a highly reactive and caustic substance. Handle the flakes and solution with extreme care and caution

    • Extended skin contact with NaOH can lead to ulceration and scarring.

    • Gloves are compulsory while handling NaOH. Add water to NaOH flakes; not NaOH flakes to water. For every gram of flakes add a minimum of 10ml of water

    • Add copper sulphate solution drop by drop

    • Handle the breakable material carefully.

    • Please do not ingest any of the materials

  1. One plastic dropper bottle contains sodium hydroxide flakes
    • One plastic dropper bottle contains sodium hydroxide flakes

    • Fill the container with water, close it, and shake well to dissolve the flakes

    • Another plastic container contains copper sulphate (CuSO4) crystals

    • Fill container with water, close it, and shake to dissolve the crystals

    • You will have CuSO4 solution in the bottle

    • Take around 3 ml of the food sample in a test tube. Here, we have taken milk.

    • Take the NaOH dropper bottle and add an equal amount of NaOH to the food sample.

    • Take the CuSO4 dropper bottle and add 5-6 drops of copper sulphate solution.

    • Repeat the test with another food sample. Here, we have taken salt water solution.

    • Observe the colour change in the food samples after adding NaOH and CuSO4

    • A deep violet colour would indicate the presence of protein

    • Conduct the test with various food items from daily life - wheat, ragi, egg, carrot, pulses, etc. Look for a pattern related to the presence of proteins in animal products and seeds of plants. Note that proteins play a key role in the growth of plants and animals.

    • What is the colour inside the saltwater test tube?

    • What about the test tube with milk/egg?

    • Vary the proportion of ingredients in each of the test tubes and see if you get the same result

    • Test other household food items for protein using the same method: cooked rice, wheat flour mixed with water, vegetable stock, chicken/meat stock etc.

    • Use the same quantity of ingredients as mentioned in the steps, except when experimenting with variations where indicated

    • Make sure the solutions are stirred and mixed well

    • Ensure the drops of copper sulphate solution mix well with the ingredients in the test tubes by gently shaking them while adding it

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