In Biuret test, the presence of ________ is indicated by violet colour.
In an experiment, Radha took small amounts of an unknown food item in a test tube. Then, she added two drops of copper sulphate solution in the test tube along with a few drops of caustic soda solution. After a few minutes, the colour of the food item changed to violet.
In the given experiment, the change in colour of the food item to violet indicates the presence of