Question

If we add copper sulphate and caustic soda to food sample solution, the color changes to violet. It shows presence of

Answer 1

Answer:

PROTEINS

Explanation:

When two drops of copper sulphate and ten drops of caustic soda or NaOH is added to  food sample solution, it turns violet. This indicates the presence of proteins.  

This is Biuret's test and the principle is simple as follows:

In the presence of alkaline medium (caustic soda or NaOH), the Cu^2+  ions get reduced to Cu+  and binds to the food sample solution proteins, thereby giving a violet color.