Short Answer Type Questions:
How can you test presence of proteins in a given food item?
Take a small quantity of the food item. If the sample is solid, grind it. Put some part of this in a clean test tube, add 10 drops of water to it and shake the test tube. Now, with the help of a dropper, add two drops of a solution of copper sulphate and 10 drops of a solution of caustic soda to the test tube. Shake well and place the test tube in a test tube stand for a few minutes.
Observe the colour of the contents of the test tube. If the colour of the contents turns violet, the food item contains protein.
Note: Copper sulphate and caustic soda solutions are harmful. Handle them with care.
Food + water + copper sulphate + caustic soda → violet colour → protein is present.