A fruit seller says that orange contain vitamin c, glucose and protein. Explain how you would test orange juice in the laboratory to find out if each of these nutrients is present

Here's how you would test orange juice for Vitamin C, glucose, and protein in the laboratory:

1. Test for Vitamin C (Ascorbic Acid)

• Reagent: DCPIP (2,6-dichlorophenolindophenol) solution.
• Procedure:
  • Add a few drops of blue DCPIP solution to a test tube.
  • Slowly add orange juice drop by drop to the DCPIP solution, shaking gently after each drop.
• Observation: If Vitamin C is present, the blue DCPIP solution will decolorize and turn colorless. The more Vitamin C present, the fewer drops of orange juice will be needed to decolorize the DCPIP.

2. Test for Glucose (Reducing Sugars)

• Reagent: Benedict's solution.
• Procedure:
  • Add about 2 mL of orange juice to a test tube.
  • Add an equal volume (about 2 mL) of Benedict's solution to the test tube.
  • Heat the test tube gently in a hot water bath (around $80^\circ \text{C}$) for 5-10 minutes.
• Observation: If glucose (a reducing sugar) is present, the blue Benedict's solution will change color, forming a precipitate that can range from green, yellow, orange, to brick-red, depending on the concentration of glucose.

3. Test for Protein

• Reagents: Sodium hydroxide (NaOH) solution and copper(II) sulfate ($\text{CuSO}_4$) solution.
• Procedure:
  • Add about 2 mL of orange juice to a test tube.
  • Add an equal volume (about 2 mL) of sodium hydroxide solution to the test tube and mix well.
  • Add a few drops of dilute copper(II) sulfate solution to the mixture and shake gently.
• Observation: If protein is present, the solution will turn violet or purple. If no protein is present, the solution will remain blue (the color of the copper(II) sulfate).