Riya wants to test a food sample for presence of proteins. Which of the following should she first add to the sample?

Options

A. Iodine solution
B. Benedict's solution
C. Ethanol
D. Copper sulphate solution

Explanation

To determine the presence of proteins in a food sample, Riya should follow these steps:

1. **Identify the appropriate reagent**: The first step is to know which reagent is used to test for proteins. The common test for proteins is the Biuret test, which requires the use of copper sulfate (CuSO4) and sodium hydroxide (NaOH).

2. **Prepare the sample**: Riya should take a small amount of the food sample she wants to test.

3. **Add sodium hydroxide (NaOH)**: Riya should first add a few drops of sodium hydroxide solution to the food sample. This is important because the alkaline environment is necessary for the Biuret test to work.

4. **Add copper sulfate (CuSO4)**: After adding NaOH, Riya should then add a few drops of copper sulfate solution to the mixture.

5. **Observe the color change**: If proteins are present in the food sample, the solution will change color to purple. If there is no protein, the solution will remain blue.

6. **Conclusion**: Based on the color change, Riya can conclude whether proteins are present in the food sample or not.